Mississippi Senator Trent Lott, the Senate's No. 2 Republican, announced Monday he will retire from the Senate by end of year.
"It's time for us to do something else," Lott said, speaking for himself and his wife Tricia at a news conference.
Lott, 66, said he had notified President Bush, Vice President Dick Cheney and Mississippi Governor Haley Barbour on Sunday about his plans. Barbour, a Republican, will name someone to temporarily replace Lott.
"There are no problems. I feel fine," Lott said.
Arizona Senator Jon Kyl, who helped broker a bipartisan immigration bill that went down to defeat this year despite President Bush's support for it, will run to replace Lott as the Republicans' vote-counting whip, said spokesman Ryan Patmintra.
Lott described his 16 years in the House and 19 in the Senate "a wild ride - and one that I'm proud of."
He said he was leaving with "no anger, no malice."
Lott's colleagues elected him as the Senate's Republican whip last year, a redemption for the Mississippian after his ouster five years ago as the party's Senate leader over remarks he made at retiring Senator Strom Thurmond's 100th birthday party. Lott had saluted the South Carolina senator with comments later interpreted as support for southern segregationist policies.
Asked about his conversation with Bush, Lott said, "He was very kind in his remarks. Over the years we've had our ups and downs, good times and bad times, both of us."
Bush did not stand behind Lott after his remarks about Thurmond, increasing pressure on the lawmaker to step down from the No. 1 Senate job.