Elections
In 2002, after briefly considering a run for governor, Thune set his sights on the U.S. Senate. He ran against incumbent Democratic U.S. senator Tim Johnson and lost by only 524 votes (0.15%). One study concluded: "While the margin of victory [for Johnson] was a mere 524 votes, getting into that winning position required a number of important factors, including Native American turnout, the ability of Johnson and his allies to more effectively use the ground war to get their message out, Thune's ineffectiveness on the air and lack of experience in winning competitive elections, low voter turnout in key Republican counties, the drought, and finally the presence of Kurt Evans. Evans, a Libertarian candidate who withdrew from the race, endorsed Thune, but remained on the ballot and siphoned away more votes from Thune than Johnson. Evans received only 3,070 votes, but that ended up being six times greater than the margin of victory." Despite the close results, Thune did not contest the election.
In 2004, Thune challenged Tom Daschle, the United States Senate minority leader and leader of the Senate Democratic Caucus. In early 2003, despite speculation, Daschle decided not to run for president the following year. CNN reported that the "announcement surprised even some of his closest aides, one of whom told CNN plans were being made for Daschle to announce his candidacy Saturday in his hometown of Aberdeen, South Dakota."
The 2004 U.S. Senate race in South Dakota was the most expensive Senate race that year, with a total of $30 million spent, and the most expensive race in South Dakota history. It was widely followed in the national media. Thune, along with Senate majority leader Bill Frist, President George W. Bush, and Vice President Dick Cheney, described Daschle as the "chief obstructionist" of Bush's agenda. "Thune was able to criticize 'Daschle for serving incompatible masters' and portray him, as Frist did when he came to South Dakota to campaign for Thune, as a partisan obstructionist and political heir to liberal icon and former Senator George McGovern of South Dakota."
Daschle's critics charged the Democrat with using filibusters to block confirmation of several of Bush's nominees to the federal judiciary and of being out of step with South Dakota voters on other political and social issues: "The GOP had targeted Daschle, the Senate minority leader, claiming he had been the chief obstruction to President Bush on such issues as tax cuts, judicial nominees and the war in Iraq."
On November 2, 2004, Thune defeated Daschle by 4,508 votes, winning 51% of the vote. Daschle's loss was the first ousting of an incumbent floor leader since 1952, when Arizona Senator Ernest McFarland lost to Barry Goldwater. The loss made Daschle "the first Senate party leader in more than five decades to be voted out of office".
South Dakota native Tom Brokaw commented that Thune "ran a very strong campaign" to win the 2004 race. University of South Dakota political scientist Bill Richardson said, "motivated John Thune supporters went to the polls in large numbers, part of a massive South Dakota turnout. Unofficial results show nearly 80 percent of registered voters cast ballots." After Thune defeated Daschle, many Republicans regarded him as a "rising star with unlimited political potential".
Thune was reelected without any opposition in either the primary or general election. Scott Heidepriem, the South Dakota Senate minority leader and a Democratic candidate for Governor of South Dakota, said, "We just concluded that John Thune is an extremely popular senator who is going to win another term in the Senate." The conservative publication Townhall commented that the absence of a Democratic candidate in the election marked "the first time in the state's modern history in which a major party has failed to field a Senate candidate".
Thune faced Democratic nominee Jay Williams, chair of the Yankton County Democratic Party. On November 8, he defeated Williams with 71.8% of the vote.
Thune "drew the wrath of Donald Trump for pushing back on the former president's false claims" that he won the 2020 presidential election. Trump called upon South Dakota governor Kristi Noem to launch a primary challenge to Thune in the 2022 U.S. Senate election in South Dakota; Noem declined. Thune also received negative feedback from Trump supporters for his position on the 2020 election. While Thune seriously considered retiring from the Senate, he announced in January 2022 that he would seek reelection to a fourth term. He was reelected with 69.6% of the vote, defeating Democratic nominee Brian Bengs.
