From 1734 until 1739 he wrote anonymously for the leading Tory periodical, The Craftsman, against the Prime Minister, Sir Robert Walpole. Fielding's patron was the opposition Whig MP George Lyttelton, a boyhood friend from Eton. Lyttelton followed his leader Lord Cobham in forming a Whig opposition to Walpole's government called the Cobhamites (which included another of Fielding's Eton friends, William Pitt). In The Craftsman, Fielding voiced the opposition attack on bribery and corruption in British politics. Although writing for the opposition to Walpole, which included Tories as well as Whigs, Fielding was "unshakably a Whig" and often praised Whig heroes such as the Duke of Marlborough and Gilbert Burnet.
Fielding dedicated his play Don Quixote in England to the opposition Whig leader Lord Chesterfield. It was published on 17 April 1734, the same day writs were issued for the general election. He dedicated his 1735 play The Universal Gallant to Charles Spencer, 3rd Duke of Marlborough, a political follower of Chesterfield. The other prominent opposition newspaper, Common Sense, founded by Chesterfield and Lyttelton, was named after a character in Fielding's Pasquin (1736). Fielding wrote at least two articles for it in 1737 and 1738.
Fielding married Charlotte Craddock in 1734 at the Church of St Mary in Charlcombe, Somerset. She died in 1744, and he later modelled the heroines of Tom Jones and of Amelia on her. They had five children; their only daughter Henrietta died at the age of 23, having already been "in deep decline" when she married a military engineer, James Gabriel Montresor, some months before. Three years after Charlotte's death, Fielding disregarded public opinion by marrying her former maid Mary Daniel, who was pregnant. Mary bore five children: three daughters who died young, and two sons, William and Allen.