WASHINGTON — Senator John Thune of South Dakota, the second-ranking Senate Republican, announced on Saturday that he would seek re-election, after an aggressive lobbying campaign by colleagues prompted him to put aside concerns about the future of his party and pursue a fourth term.
“I’m asking South Dakotans for the opportunity to continue serving them in the U.S. Senate,” Mr. Thune, the minority whip, said in a statement, adding that he could deliver for his state.
“I am uniquely positioned to get that job done,” he said.
The South Dakotan, who turned 61 on Friday, had recently told associates that he was considering retirement, complaining about the strain of congressional service and privately expressing concern about former President Donald J. Trump’s continuing grip on the Republican Party.
But by seeking re-election in a heavily conservative state, Mr. Thune is well positioned to win again and potentially succeed Senator Mitch McConnell of Kentucky, the minority leader, as the Senate’s top Republican.
A host of Senate Republicans leaned on Mr. Thune in recent weeks to run again, but Mr. McConnell was especially aggressive and met privately with him this past week. The Kentucky Republican turns 80 next month and has made clear that he wants to remain his party’s Senate leader into 2023, when he would become the longest-serving party leader in the chamber’s history.
It is unclear how long Mr. McConnell will serve beyond then, though, an open question that helped lure Mr. Thune to seek another term. Mr. Thune has told associates he is confident he would have the support to succeed Mr. McConnell when the leader exits.
The South Dakotan would face competition for the post, however. Senator John Cornyn of Texas preceded Mr. Thune as the party whip and has indicated his interest in succeeding Mr. McConnell, as has Senator John Barrasso of Wyoming, currently the No. 3 Republican.
For now, Mr. Thune will have to navigate re-election in South Dakota, which rejected its two most famous senators, George S. McGovern and Tom Daschle, both Democrats, in their bids for fourth terms.
Mr. Thune’s only real obstacle, though, would be a primary. He put off a decision on running until the new year because he wanted to minimize the time a potential Republican rival would have to mount a primary challenge — and to limit Mr. Trump’s window for mischief-making.
The former president lashed out at Mr. Thune at the end of 2020 after the senator said Mr. Trump’s unfounded election objections would go down “like a shot dog” in the Senate.
That prompted the former president, who maintains an iron grip on the Republican Party and has already intervened in a series of 2022 primaries to consolidate his power even further, to deride Mr. Thune as “Mitch’s boy” and a “RINO,” or a Republican in name only.
“He will be primaried in 2022, political career over!!!” Mr. Trump warned at the time.
But no major primary challenger has emerged. And Mr. Trump’s allies in the Senate said last month that the former president would be unlikely to oppose Mr. Thune if the senator appeared likely to win renomination.
Once a hub of prairie populism, South Dakota has turned deeply red in the last two decades, a transition that began with Mr. Thune’s defeat of Mr. Daschle in 2004.