With a dozen races still to be called, the G.O.P. was two seats away from the 218 that would allow the party to claim a coveted governing trifecta: control of the House, Senate and White House.

It was the first seriously contested Senate Republican leadership election in decades. Three senators were competing to succeed longtime GOP leader Mitch McConnell of Kentucky, when he steps down from the post at the beginning of next year and Republicans take back the Senate majority.