The growing prospect that the Democrats may recapture the House, Senate, or both is creating lots of job insecurity for congressional leaders.

The Democratic and Republican caucuses in both chambers may toss out their current leaders and install fresh blood if November sees a strong Democratic showing.

Senate Republicans. A change of leaders is certain with majority leader Bill Frist of Tennessee giving up his seat for a likely presidential run in 2008.

The number-two Republican, Mitch McConnell of Kentucky, claims to have most Republican votes sewn up. But in a secret-ballot election, a colleague’s private promise is about as secure as a New Orleans levee. Look for a comeback bid by former majority leader Trent Lott of Mississippi, who was forced to resign in 2002 when he seemed to be pining for the days of segregation. Lott has since sought redemption more times than Tammy Faye Bakker.

Senate Democrats. Minority leader Harry Reid of Nevada has a reputation for over-the-top attacks. He called President Bush a “loser” and former Federal Reserve chair Alan Greenspan a “hack.” Plus, Reid has political ties to lobbyist Jack Abramoff. Still, Reid is a savvy student of Senate rules, has kept his caucus united, and is an effective partisan slasher.

If the Dems win the Senate and want to project a cleaner image, Reid might very well get the heave-ho. The Democratic whip, Dick Durbin, is less acerbic and more congenial. New York’s Charles Schumer is another possibility. He’d put in the long hours, particularly if it means more television exposure.

House Republicans. If the GOP loses a lot of House seats—even if it hangs on to control—members will push for new leadership.

Speaker Dennis Hastert is well liked but lacks the energy and imagination to plot a comeback. He might be kept as a figurehead leader, but John Boehner of Ohio, who replaced Tom DeLay as majority leader, stands a good chance of being ousted if the Republicans do poorly. Possible successors include ambitious lawmakers Mike Pence of Indiana and Eric Cantor of Virginia.

House Democrats. If the Dems capture the House, current minority leader Nancy Pelosi of California could become the first female Speaker and second in the line of presidential succession.

But many colleagues are worried about having an ultra-liberal from San Francisco be the face of the party going into 2008. And she’s not that well liked personally.

House Democrats might prefer her deputy, Steny Hoyer of Maryland, a nuts-and-bolts pol. Trouble is, he’s so colorless, he makes Hastert look like a party animal. So the Democrats could tap one of their old bulls for Speaker, such as John Dingell of Michigan or Californians Henry Waxman or George Miller.