In January, U.S. Sen. Harry Reid (D-Searchlight) will have two years under his belt as Senate majority leader. There's no particular reason to suspect that his reign is nearing an end, but recent majority leaders have served short terms, and sometimes hit dead ends in their political careers.

U.S. Sen. Bill Frist (R-Tenn.) served for four years as majority leader and then walked away from the Senate. U.S. Sen. Tom Daschle (D-S.D.) was majority leader for two years before being defeated during his next re-election campaign. It's not a major concern yet, but like South Dakota, the Nevada media market is not terribly expensive, and could present a similar opportunity for Republicans under the right conditions.

After a total of five years, U.S. Sen. Trent Lott (R-Miss.) resigned from the leadership post in the wake of a Strom Thurmond controversy. After less than two years as majority leader (the second time), U.S. Sen. Bob Dole (R-Kan.) left the Senate to run for president. After leading the Senate for six years, U.S. Sen. George Mitchell (D-Maine) chose not to run for re-election.