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.

After 18 years of Mitch McConnell, Senate Republicans officially have a new top dog: South Dakota Senator John Thune will step into the Majority Leader role at the beginning of next year, after being selected by his colleagues Wednesday.

Two decades after John Thune ignited his political brand by knocking off Democratic Senate Leader Tom Daschle in South Dakota’s momentous 2004 U.S. Senate race, he will assume the Republican leadership role himself.