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 Mitch McConnell into a key position as President-elect Donald Trump returns to the White House.

U.S. Senate Republicans will gather behind closed doors on Wednesday to pick their next leader in the face of a public pressure campaign by supporters of President-elect Donald Trump who favor the long-shot bid of a hardline Trump loyalist.

In the first seriously contested Senate Republican leadership election in decades, three senators are vying to replace longtime GOP leader Mitch McConnell when he steps down from the post at the beginning of next year.