It’s been a long time coming this election season, but the first congressional incumbents have finally been defeated at the polls – three of them in one night. Sen. Joe Lieberman (D-Conn) got nearly all the media attention as he was beaten by newcomer Ned Lamont in Connecticut – though Lieberman vowed to keep fighting and said he would run in the fall as an independent.

On the same night, Cynthia McKinney (D-Ga) lost a runoff in her Georgia primary. And moderate Republican freshman Joe Schwarz (R-Mich) was upended by a more conservative challenger in the Michigan GOP primary.

Prior to yesterday’s votes, the only incumbents to drop reelection bids this year did so on their own, before the voters could decide. The most recent of those was Bob Ney (R-Ohio), a central figure in the Abramoff lobbying scandal, who announced on Monday he would withdraw from his race and not seek another term.

On the surface, the three incumbents who lost yesterday seem to have virtually nothing in common. The Lieberman race was a referendum on his support of President Bush’s handling of the increasingly unpopular Iraq war. Schwarz, on the other hand, was supported by President Bush, but was targeted from the right for being more liberal than his district. McKinney’s race was an odd one. Long an outspoken critic of the president, she was also criticized for occasionally erratic behavior – most especially this spring when she was arrested (though later cleared) on charges that she assaulted a guard at the Capitol who tried to stop her when she skipped past a metal detector.

In short, except for Lieberman’s race, the other contests seemed to be decided on local issues, not some national wave of discontent. But something had to be in the air for three incumbents’ heads to roll in one night.

What I take it to mean is that voters are unusually restive this year, and that unease is increasing as we get closer to the fall elections. Recent polls are picking up strong vibes that the public wants to shake things up in Washington, even at the cost of cutting short a few congressional careers.

Granted, every race is different. But if I were running for Congress this year “More of the Same” is a slogan I would avoid.