WASHINGTON — Republicans have elected South Dakota Sen. John Thune as the next Senate majority leader, completing a momentous shift in their leadership that elevates a top deputy of Sen. Mitch McConnell into a key position as President-elect Donald Trump returns to the White House.

Thune, who is 63 and in his fourth Senate term, has promised to work closely with Trump despite differences the two have had over the years. Thune will be a crucial part of the incoming president’s efforts to push through his policy agenda.

He beat out two other competitors, Sens. John Cornyn of Texas and Rick Scott of Florida, by gaining majority support from GOP senators in a secret ballot vote.

Republicans are replacing Kentucky’s McConnell, the longest serving Senate party leader, as they prepare to take majority control with the 53 seats they won in last week’s elections.

Like McConnell, Thune hails from the Republican Party’s more traditional wing. He has held the Republican whip position — the No. 2 in party leadership — since 2019.

At times, Thune has countered Trump’s wishes for Congress, and he broke publicly with Trump over the effort to overturn the results of the 2020 presidential election. But in recent months, Thune has realigned with Trump, and the two have been consulting on how to implement the incoming president’s agenda.