The wintertime departure from Congress of Sen. Trent Lott is heating up a political environment already stickier than Mississippi in summertime.

The second most powerful Republican in the Senate announced on Nov. 26 that he would resign his Mississippi seat by the end of the year, stunning even close advisers: Lott was just one year into the six-year term he won by reelection last November. He has served in Congress nearly 35 years.

Lott is the sixth Republican senator to announce his retirement this year. In the House, 17 Republicans have said they would leave. Lott's retirement plans raised immediate questions: Why is he leaving? Who will replace him? And what will a slew of Republican retirements mean for a fragile congressional balance during next year's elections?

Lott offered few specifics for his retirement. The senator told reporters he wanted to spend more time with his family and "do something different" with his life, but said his future plans weren't settled.

One day later, Chester Lott, the senator's son, confirmed what many suspected: The senator is considering a lobbying career, he said. That may explain why Lott says he'll leave by Dec. 31. On Jan. 1 new rules take effect that require senators to refrain from lobbying former colleagues for two years from the time they left office. A New Year's Eve departure would exempt Lott from a waiting period.

During a press conference in Pascagoula, Miss., Lott, 66, alluded to a deeper reason for leaving: battle fatigue. "I've been in the majority and I've been in the minority, back and forth, six times," Lott said. "And if I were 20 years younger, I'd be mounting my horse saying, 'Let's get this majority back.'"

It will be up to Mississippi's Republican governor, Haley Barbour, to decide who mounts the horse next. Barbour said he would appoint an interim replacement for Lott within 10 days of his formal resignation and would call a special election on Nov. 8, 2008, to determine a successor for the remainder of Lott's term.

(Mississippi Attorney General Jim Hood argued that state election laws might require the governor to call an election much sooner, setting up a potential legal showdown during a critical election year.)

Two Mississippi congressmen are considered leading candidates for the Senate appointment: Republican representatives Charles "Chip" Pickering Jr. and Roger Wicker.

Other Republicans are pushing for Barbour to appoint Pickering's father, retired federal judge Charles Pickering. President George W. Bush nominated the senior Pickering for a federal appeals court post in 2002, but Democrats blocked the nomination.

Appointing a Republican who can keep the Senate seat in an election will be crucial for the GOP's efforts to keep Democrats from gaining a larger majority in Congress next year. (The Senate is divided evenly between 49 Republicans and 49 Democrats. Two independents typically vote with Democrats, tipping the fragile balance in their direction.)

Mississippi voters usually favor Republicans, but in three other states where Republican senators are retiring the balance could shift: Democrats are favored to take races in Virginia, Colorado, and New Mexico.

So far, Democrats look determined to keep their seats: No Senate Democrat up for reelection next year has announced plans to retire.

Goodbye

Senate

Six Senate Republicans are retiring:

Wayne Allard (Colo.)

Larry Craig (Idaho)

Pete Domenici (N.M.)

Chuck Hagel (Neb.)

Trent Lott (Miss.)

John Warner (Va.)

No Senate Democrats are retiring.

House of Representatives

17 Republicans are retiring or running for higher offices:

Barbara Cubin (Wyo.)

Terry Everett (Ala.)

Mike Ferguson (N.J.)

Dennis Hastert (Ill.)

David Hobson (Ohio)

Duncan Hunter (Calif.)

Ray LaHood (Ill.)

Steve Pearce (N.M.)

Chip Pickering (Miss.)

Deborah Pryce (Ohio)

Jim Ramstad (Minn.)

Ralph Regula (Ohio)

Rick Renzi (Ariz.)

Jim Saxton (N.J.)

Tom Tancredo (Colo.)

Heather Wilson (N.M.)

Jerry Weller (Ill.)

In addition, Bobby Jindal is resigning his House seat to serve as governor of Louisiana.

Five House Democrats are retiring or running for higher offices:

Tom Allen (Maine)

Julia Carson (Ind.)

Michael McNulty (N.Y.)

Mark Udall (Colo.)

Tom Udall (N.M.)