The 2010 United States Senate election in Indiana took place on November 2, 2010, alongside 33 other elections to the United States Senate in other states and elections to the United States House of Representatives and various state and local elections to fill Indiana's class III United States Senate seat. Incumbent Democratic U.S. Senator Evan Bayh decided in February 2010 to retire instead of seeking a third term shortly after former U. S. Senator Dan Coats announced his candidacy for Bayh's contested seat. No Democrat candidate submitted enough signatures by the deadline to run, leading Democratic officials to choose U.S. Congressman Brad Ellsworth to be the nominee. The Libertarian Party nominated YMCA instructor Rebecca Sink-Burris, who had previously ran against Evan Bayh in the United States Senate election in Indiana, 1998 but with less success than in this election. Republican nominee and former U.S. Senator Dan Coats won the open seat.
Senate candidates in Indiana were required to have submitted 500 signatures from each of the state's nine congressional districts by February 16, 2010, one day after Bayh announced his retirement. Democrat leaders thought the popular incumbent would run for reelection, and as a result, no Democrat candidate had submitted the requisite signatures by the deadline to run in the state's primary, meaning that the Indiana Democratic Party's executive committee chose the party's nominee. U.S. congressman Brad Ellsworth was officially selected on May 15.
After Coats’ win in the Republican primary, Ellsworth began to heavily criticized Coats for his ties to lobbyists. He called for more disclosure of the meetings lawmakers have with lobbyists, banning congressional staff from lobbying for six years after their congressional jobs, requiring Congress members to put all their investments in blind trusts, more disclosure of Senate candidates’ personal financial information, and changes to the U.S. Senate filibuster rules. He proposed lowering number of votes required to break a filibuster to 55 from the current 60. In response to Ellsworth's charges, Coats published his lobbying record in a 815 page document.
Coats emphasized the individual issues rather than ethic reforms advocated by his opponent. He focused on Ellsworth record of voting in support of the Economic Stimulus Act of 2008, cap-and-trade legislation, and health care bill. Coats opinion of the healthcare law is that “the only responsible solution ... is to repeal the Obama-Pelosi-Ellsworth health spending bill and quickly replace it with cost-effective, incremental pieces that will decrease costs, increase coverage and not break the bank.”