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.

The election of Republican Sen. John Thune of South Dakota as the next leader of his party in the chamber – putting him on track to become Senate majority leader next year – tasks a key ally of Mitch McConnell with shepherding the agenda of President-elect Donald Trump through Congress.