When the new U.S. Congress convenes in January, Mitch McConnell becomes Senate majority leader, fulfilling a long-held ambition.
A Senate Republican official said McConnell, 72 , was chosen by acclamation at a closed-door meeting of the party rank and file.
As majority leader, one of the most powerful positions in Congress, McConnell will set the Senate's agenda. Along with Republican House Speaker John Boehner, he will decide what legislation is sent to the White House in the final two years of President Barack Obama's term.
McConnell was elected to a sixth Senate term of six years last week in elections in which Republicans gained a majority in the 100-member Senate for the first time in eight year, picking up eight seats from Democrats and hoping for a ninth in a Louisiana runoff election Dec. 6.
Democrats have assailed him in recent campaigns as a guardian of gridlock for his opposition to nearly all of President Barack Obama's initiatives. But he also brokered bipartisan deals that ended last year's government shutdown and averted a 2011 federal default.
Democrats had hoped to defeat him but he outpaced his opponent in the final weeks of the campaign for the seat from the state of Kentucky.
McConnell is a conservative and does not have much charisma. But his 30 years in the Senate have made him a masterful political tactician. One of his challenges will be keeping in line conservative tea party Republicans who would like to see him take a more hard-line position on some issues.
Neither McConnell nor Boehner faced public opposition on the eve of Thursday's party elections in closed door meetings.
Boehner, 65, is line to become leader of the House for a third term, also one of the pre-eminent positions in the capital's political life. Like McConnell, his years in the lower chamber have made him skilled in legislative maneuvering and he also has had difficulties in the past keeping the more conservative Republican members of the House in line.
The Republicans also padded its majority in the 435-member House, where a handful of races remain unresolved. Republicans are on track to equal or eclipse the 246 seats they won in 1946, a figure that stands as a post-World War II high.
Despite sizable election losses, Democrats appeared ready to hand their own leaders another two years at the helm, postponing a generational change that appears not far in the future.
Sen. Harry Reid, a few weeks shy of his 75th birthday, was in line to become the minority leader in the new Congress. He was first elected Democratic leader in 2004.
Officials said Sen. Elizabeth Warren, a favorite of liberals and mentioned as a possible rival to Hillary Rodham Clinton for the party's 2016 presidential nomination, would be given a seat at the leadership table.
Rep. Nancy Pelosi , 74, is expected to be elected to a new term as House Democratic leader when the rank-and-file meets next week. She first won her post a dozen years ago. She was speaker for four years when Democrats held the majority, and has served as minority leader for eight.