Coleman attended Brooklyn Law School from 1972 until 1974 but received his Juris Doctor from the University of Iowa College of Law in 1976.

Coleman married actress Laurie Casserly in 1981. The couple have two children, Jacob and Sarah. Two other children died during infancy (Adam, 1983; Grace, 1992) from a rare genetic disorder known as Zellweger syndrome. In 2016, Jacob Coleman announced his candidacy for an open state senate seat held by Julianne Ortman, but did not win the Republican endorsement and chose to support the endorsed candidate.

One of Coleman’s accomplishments as mayor of Saint Paul was to bring professional ice hockey back to Minnesota. In 1993 the Minnesota North Stars moved to Dallas, Texas. On June 7, 1997, the NHL awarded Saint Paul an expansion franchise, later named the Minnesota Wild, that would play in a new arena downtown at the site of Civic Center Arena. The new arena, later named the Xcel Energy Center, was built through a public-private partnership, with $65 million from state taxpayers and $30 million from the city of Saint Paul.

While running for mayor in 1993, Coleman wrote in a letter to the City Convention Delegates: “I have never sought any other political office. I have no other ambition other than to be mayor.” In the letter he wrote:

While many praised him for his “pragmatic” leadership style and successes in revitalizing St. Paul, critics labeled him an “opportunist” and Coleman frequently found himself at odds with the Democratic Party’s more liberal members. In 1996 he was sometimes booed at party events or excluded from them altogether.

Coleman joined the Republican Party in 1996 and was reelected mayor of St. Paul in 1997, defeating Democratic-Farmer-Labor Party nominee State Senator Sandy Pappas. He is, as of 2020, the last Republican mayor of St. Paul.

In 1996, Coleman chaired Wellstone’s Senate reelection campaign. In his nomination speech at the 1996 state DFL convention, Coleman said, “Paul Wellstone is a Democrat, and I am a Democrat.” Tensions were so high between Coleman and the DFL party at the time that a number of convention delegates loudly booed Coleman’s speech.

In December 1996, Coleman announced he was leaving the DFL to join the Republican Party. He cited his frustrations with the Democratic Party and his belief that the Republican Party offered the best chance to continue his efforts to hold the line on taxes and grow jobs.

Coleman’s critics, mostly DFL party leaders, speculated that his switch was motivated by his aspirations to statewide office. As an abortion opponent and a frequent adversary of public employee unions, Coleman was at odds with the DFL leadership in Minnesota. In a letter to supporters announcing the switch, he wrote, “while the political party I belong to changes, nothing about how I govern or what I believe changes at all.” He was reelected mayor of St. Paul in 1997 with nearly 60% of the vote.

Coleman’s role in bringing professional hockey back to Minnesota and his popularity in St. Paul helped fuel a run for governor in 1998. He easily secured the Republican nomination, facing just token opposition in the primary. He faced DFL candidate Hubert H. “Skip” Humphrey III and Reform Party candidate Jesse Ventura in the general election. Polls had Coleman and Humphrey running even, but Ventura won the election in an upset.

As mayor Coleman refused to sign a city proclamation celebrating the annual gay pride festival, explaining his opposition: “What we have had in St. Paul and Minneapolis for many years is signing a joint proclamation making it gay/lesbian/bisexual/transgender month. I will say that I support human rights … And of course that includes sexual orientation. On the other hand, I’ve felt very strongly that it wasn’t government’s responsibility to give proclamations for people’s sexuality. I don’t think government has a responsibility to issue awards for one’s sexuality.” Coleman hired Susan Kimberly, a trans woman, as deputy mayor in 1998. Kimberly also worked as state legislative director in Coleman’s Minnesota Senate office.

Coleman made plans for a second run for governor in 2002, but Karl Rove and George W. Bush persuaded him to challenge incumbent Senator Paul Wellstone in that year’s election instead. Coleman easily won the Republican nomination.

Coleman opposes recognition of same-sex marriages by either the federal or state governments. In his 2002 Senate campaign he pledged support for an amendment to the United States Constitution that would ban any state from legalizing same-sex marriage. In 2004 and 2006 he voted in favor of such an amendment.

In 2002, the Bush administration persuaded Coleman to run against Wellstone rather than for governor.

In April 2003, Coleman told a Capitol Hill reporter that he was a “99% improvement” over Wellstone because he had a better working relationship with the White House. Many Wellstone supporters found this offensive and insulting, and at least one member of Congress urged Coleman to apologize. Coleman issued an apology, explaining that he was referring specifically to the reporter’s question about the differences between his and Wellstone’s relationship with the White House, and saying in part, “I would never want to diminish the legacy or memory of Senator Paul Wellstone, and I will accept full responsibility for not having been more accurate in my comments.” In 2004 Coleman campaigned for the chairmanship of the National Republican Senatorial Committee (NRSC), but was defeated for the post by North Carolina Senator Elizabeth Dole in a 28–27 vote.

Coleman is a member of the Freemason fraternity, having been made a Mason at sight in 2003 by then Grand Master of Masons in Minnesota Neil Neddermeyer.

In 2005, Coleman led a bipartisan coalition of 34 senators in securing a renewable fuels package as part of the 2005 Energy Policy Act, which included new standards for renewable fuels and an extension of tax credits for biodiesel, small ethanol producers and wind and livestock waste.

On December 11, 2005, Coleman voted in favor of invoking cloture on, thus advancing, a defense appropriations bill that included oil exploration in the Arctic National Wildlife Refuge. Critics viewed this as a violation of his pledge to oppose such drilling. Coleman said he did so because although he planned to vote against the bill, he did not believe that a filibuster was warranted. His vote notwithstanding, the filibuster held, and Coleman voted to strip the ANWR provision from the bill in a subsequent vote.

Coleman expressed reservations about supporting DR-CAFTA (Dominican Republic – Central America Free Trade Agreement) unless the interests of the domestic U.S. sugar industry (including Minnesota’s sugar beet industry) were accommodated. He voted in favor of DR-CAFTA after obtaining quotas imposed on foreign sugar until 2008. He stood behind President Bush on August 2, 2005, as the trade agreement was signed into law. “This is a 3-year insurance policy that I have purchased for my sugar farmers,” he said.

In December 2005, Coleman voted for a budget bill that cut funding from a number of programs but kept funding for sugar beet farmers in Minnesota after Rove asked him to support the administration’s position on the issue. Coleman told Congress Daily that he would not vote for a bill that cut sugar beet funding but “Karl Rove called me and asked what I wanted. A few hours later it was out of the bill.”

In May 2005, the Senate’s Permanent Subcommittee on Investigations, chaired by Coleman, held hearings on their investigation of abuses of the UN Oil-for-Food program, including oil smuggling, illegal kickbacks and use of surcharges, and Saddam Hussein’s use of oil vouchers to buy influence abroad. These Oil-for-Food Program Hearings covered corporations (including Bayoil) and several well-known political figures of various nations (including Vladimir Zhironovsky), but are best remembered for the confrontational appearance of British politician George Galloway, then a Member of Parliament for the RESPECT The Unity Coalition (Respect). Coleman accused Galloway of abuses that Galloway provably denied.

Coleman has campaigned as an anti-abortion candidate since at least 1993. He attributes this position to the death of two of his four children in infancy from a rare genetic disease. He supports limiting stem cell research to adult stem cells and stem cells derived from umbilical cord blood, and in July 2006 voted against lifting restrictions on federal research dollars for new embryonic stem cell lines. Coleman is a member of the Republican Main Street Partnership, which supports embryonic stem cell research. He voted in favor of legislative intervention to prolong the life of severely brain-damaged Floridian Terri Schiavo.

On March 14, 2006, Coleman called on Bush to replace or reorganize his staff, saying that they did not sufficiently have their “ears to the ground” on matters like Hurricane Katrina, Harriet Miers’s failed Supreme Court nomination, and the Dubai Ports World controversy, and accusing the administration of having a “tin ear.” He said they showed inadequate “political sensitivity” in their handling of the issues.

The previous year, Coleman had called on UN Secretary-general Kofi Annan to resign for other alleged program abuses. On June 2, 2006, Coleman responded to criticism that he had insufficiently investigated the Australian Wheat Board (AWB) for sanctions busting, saying that there were legal and cost hurdles. Then Prime Minister of Australia, John Howard, was a supporter of the invasion of Iraq. The Australian ambassador to the U.S., Michael Thawley, met with Coleman in late 2004 to lobby against any investigation of AWB.

On February 10, 2006, in a meeting of the Senate Committee on Homeland Security and Governmental Affairs of which Coleman was a member, during testimony of former Federal Emergency Management Agency (FEMA) director Michael D. Brown, Coleman attacked Brown for poor leadership during Hurricane Katrina disaster relief efforts, saying, “you didn’t provide the leadership, even with structural infirmities”, “you’re not prepared to kind of put a mirror in front of your face and recognize your own inadequacies”, and “the record reflects that you didn’t get it or you didn’t in writing or in some way make commands that would move people to do what has to be done until way after it should have been done.” Brown responded combatively, “well, Senator, that’s very easy for you to say sitting behind that dais and not being there in the middle of that disaster, watching that human suffering and watching those people dying and trying to deal with those structural dysfunctionalities”. and implored Coleman to stick to questions. He later likened Coleman’s charges to a “drive-by shooting.” Brown had recently said that he notified the Department of Homeland Security and the White House of the tremendous scale of Katrina flooding earlier than had been previously reported.

On March 14, 2006, Coleman introduced a bill that would ban foreign companies from operating ports in the United States.

Coleman was a member of the Republican Main Street Partnership. In March 2007 National Journal ranked him the fourth most liberal Republican in the Senate. GovTrack, an independent tracking website, also described Coleman as a “moderate Republican”.

Coleman co-sponsored several pieces of legislation to increase sanctions on Iran, including divestment of American pension funds in companies that do business with Iran and sanctions against countries that provide it with nuclear technology. In 2007 Coleman said, “For the sake of our national security, the U.S. must ensure that the sensitive nuclear technology that we share with partner countries does not fall into the hands of the Iranians.”

On January 22, 2007, Coleman and fellow Republican Senators John Warner and Susan Collins joined Democrats in opposing Bush’s planned troop increase in Iraq.

In March 2007, Coleman introduced legislation (S. 754) to kill the Defense Travel System, a program intended to automate the purchasing of travel services by the U.S. Department of Defense, which accounts for more than half of the federal government’s total outlays of around $11 billion annually for travel, including transportation, lodging, and rental cars. Shortly after he filed the legislation, Coleman received a generous contribution from the CEO of Carlson Companies, which owns Carlson Wagonlit Travel, a business travel management firm whose CW Government Travel unit provides travel management services for some federal agencies. The Carlson Companies are based in Minnesota. Over the years, Coleman has received tens of thousands of dollars in campaign donations from people connected with Carlson Companies.

In 2008, Coleman’s opponents for reelection were Dean Barkley and the DFL nominee, former Air America host and comedian Al Franken. On the day after the election, Coleman led in votes and claimed victory in the race. Minnesota law requires an automatic recount when the margin between the leading candidates is less than 0.5% of the vote, and the margin between Coleman and Franken was about 0.01%. Barkley came in third with 15%.

The initial results of the recount put Franken ahead by 225 votes out of almost 2.9 million votes cast. On December 24, 2008, Coleman’s lawyers said it was a “virtual certainty” that he would contest the results of the election.

While running for reelection in 2008, Coleman was mentioned in a Texas lawsuit by Paul McKim, CEO of Deep Marine Technology (DMT), against Nasser Kazeminy. Kazeminy was a longtime Coleman supporter who owned a controlling share of DMT. The petition alleged that Kazeminy had used DMT to funnel $75,000 or more to Laurie Coleman through her employer, Hays Companies, in order to enrich Senator Coleman. McKim’s petition covered several issues, of which the Coleman matter was only one. Coleman’s 2009 Senate financial disclosure form disclosed that Laurie Coleman received a salary from Hays Companies, but Senate rules do not require the salary amount to be revealed. Neither Coleman nor his wife was named as a defendant in the suit. On October 31 a related suit was filed in Delaware Chancery Court by minority shareholders in DMT. The Delaware suit also alleged that Kazeminy had used DMT to funnel unearned funds to Laurie Coleman through Hays Companies. As in the Texas case, the Colemans were not named as defendants.

In September 2008 Coleman joined the bipartisan Gang of 20, which was seeking a solution to the American energy crisis. The group pushed for a bill that would encourage state-by-state decisions on offshore drilling and authorize billions of dollars for conservation and alternative energy.

As a member of the Senate’s Agriculture Committee, Coleman played an important role in agriculture policy. In 2008 he helped author the Farm Bill. Coleman was praised for his efforts to improve the bill’s provisions with regard to sugar, a mainstay of northwestern Minnesota’s economy, as well as the bill’s dairy program. Coleman also worked for the inclusion of a permanent agriculture disaster assistance program and hailed the bill’s investments in conservation, nutrition, and renewable energy. Coleman broke with his fellow Republicans in several instances over agriculture policy, notably by voting for the bill to move forward, and ultimately played a critical role in breaking the stalemate that had delayed Senate consideration of the bill.

Coleman was a strong supporter of the Iraq War from the start. In 2008, he was still a supporter of the war, generally tending to agree with the Bush administration. He was in favor of the eventual removal of U.S. troops from Iraq, but did not support any kind of timetable for their removal until the situation stabilized. An August 2008 MinnPost article summarized his position as: “He believes the prospects are good for a drawdown of U.S. troops, but it must be done based on conditions on the ground as reported by commanders in the field, not according to an ‘arbitrary’ timetable set for ‘political’ reasons in Washington.”

Coleman’s term expired on January 3, 2009. On January 5, Franken was certified as the winner of the recount by 225 votes. Coleman filed a legal challenge of the results on January 6, and a three-judge panel was seated.

In January 2009 Coleman became an adviser to and board member of the Republican Jewish Coalition.

On September 11, 2009, Coleman announced he had been diagnosed with Bell’s palsy. Doctors told him that he should fully recover from it.

After sitting Minnesota Governor Tim Pawlenty announced that he would not seek reelection in 2010, it was widely anticipated that Coleman would run for governor. Polls in late 2009 showed him as the favorite among Republicans. But on January 17, 2010, Coleman announced that he would not run, saying, “The timing on this race is both a bit too soon and a bit too late. It is too soon after my last race and too late to do a proper job of seeking the support of delegates who will decide in which direction our party should go. The commitments I have to my family and the work I am currently engaged in do not allow me to now go forward.” In 2010 Coleman became chairman and CEO of the American Action Network, which he co-founded.

Coleman was considered a front-runner for the Republican National Committee’s chairmanship. He said he would not run against Michael Steele should Steele seek reelection to that position; when Steele announced his candidacy for reelection in December 2010, Coleman said that he would not run for the chairmanship. In April 2011 Coleman joined Hogan Lovells, an international legal practice, as senior government advisor in its Washington D.C. office.

In June 2011 the U.S. Justice Department decided not to file charges against Coleman or Kazeminy. Louis Freeh, an attorney for Kazeminy and a former FBI Director in the Clinton Administration, said he learned the Justice Department had ended the investigation in a February 24 meeting with Andrew Levchuk of the department’s Public Integrity Section in Washington.

On August 14, 2018, Coleman announced that cancer he had been battling in his neck and throat had spread to his lungs.

Coleman stepped down as leader of the Government Relations and Public Affairs practice at Hogan Lovells in January 2020, but remains a senior counsel.