US diplomatic cables leaked in 2011 revealed that during a 9 September 2009 meeting, former Deputy Prime Minister and "close Thaksin ally" Sompong Amornvivat told Ambassador to Thailand Eric John that he did not envision a big role for Yingluck in the Pheu Thai Party, and that "Thaksin himself was not eager to raise her profile within the party, and was more focused on finding ways to keep his own hand active in politics." However, in a subsequent cable dated 25 November 2009, the ambassador noted that in a meeting with Yingluck, she spoke with confidence about the "operations, strategy and goals" of the Pheu Thai party and seemed "far more poised" than in previous meetings. The cable cited Yingluck saying that, "Someone could easily emerge relatively late in the game to take the reins of the party and serve as the next Prime Minister."
On 16 May 2011, the Pheu Thai party voted to name Yingluck as their top candidate under the party-list system (and presumably be the party's nominee for Prime Minister) for parliamentary election scheduled for 3 July. However, she was not made party leader and did not join the party's executive board. The ultimate decision was made by Thaksin himself. "Some said she is my nominee. That's not true. But it can be said that Yingluck is my clone... Another important thing is that Ms Yingluck is my sister and she can make decisions for me. She can say 'yes' or 'no' on my behalf," noted Thaksin in an interview.
The 2011 rainy season saw the highest levels of rainfall in Thailand in the previous 50 years. Flooding started in northern Thailand on 31 July, a week prior to Yingluck's appointment as Prime Minister. Flooding quickly spread from the North to the Central Chao Phraya River Basin, and by the beginning of October, the province of Ayutthaya, north of Bangkok, was almost flooded. The floods were the worst in Thailand in over 50 years. Yingluck established centralised flood monitoring and relief operations in mid-August and made tours of flooded provinces beginning 12 August. Yingluck also pledged to invest in long-term flood prevention projects, including the construction of drainage canals. Flood reduction measures were hampered by disputes between people on the different sides of flood barriers: those on the flooded side in some instances sabotaged the barriers, sometimes resulting in armed confrontation. Opposition leader Abhisit Vejjajiva and military leaders called for Yingluck to declare a state of emergency, claiming that it would give the military greater authority to deal with embankment sabotage. A state of emergency had last been declared in 2010 during the Abhisit-government's crackdown on anti-government protesters. Yingluck refused to declare a state of emergency, saying that it would not improve flood management. Instead, she invoked the 2007 Disaster Prevention and Mitigation Act and issued a disaster warning which gave her government greater authority to manage flood control and drainage.