Washington ? The usual political torpor of August was shattered this week by the news that three congressional incumbents had lost their races in a single day. There were special forces at work in the contests that saw the defeats of two Democrats, Connecticut Sen. Joe Lieberman and Georgia Rep. Cynthia McKinney, and Michigan Republican Rep. Joe Schwarz. But taken together, they are the strongest signal yet of voter dissatisfaction with the status quo in Washington.

McKinney, a combative politician, lost (for the second time in her career) largely because of her unpleasant personality. Schwarz, a physician and freshman congressman who had headed the John McCain forces in Michigan, fell victim to a heavily financed right-wing effort to punish him for his support of stem cell research.

The “shake up Washington” theme was explicit in millionaire businessman Ned Lamont’s 52 percent to 48 percent defeat of Lieberman, the 2000 Democratic vice presidential candidate, in the headline event of the day, the Connecticut Democratic primary. Lieberman could claim 18 years of Senate seniority and long service in state government, a reputation for personal integrity, prominence on both foreign and domestic issues, and the active support of his party leaders from Bill Clinton on down.

But when I went to Connecticut three weeks before the primary, it was evident that he was going to be overwhelmed by the passion to “send a message” through Lamont of frustration with the war in Iraq, the Bush presidency and Congress.

Lieberman, as I wrote, represented a candidacy, while Lamont embodied a cause – and it was clear that the cause would prevail.

But for how long is a question. Lieberman has filed signatures for a place on the November ballot as an independent, and has vowed to make the race, no matter how many in his party urge him to drop the fight. And it need not be futile. Rep. Chris Shays, the Connecticut Republican whose seat is a target for the Democrats this year, told me the morning after the primary that he is supporting Lieberman and thinks he can win a three-way race against Lamont and the weak Republican challenger, Alan Schlesinger. Other prominent Republicans are also poised to back Lieberman and raise money for him.

In the primary, Lamont found his most prominent support on the far-left flank of the Democratic Party. His organization was a hand-me-down from the Howard Dean presidential campaign, bolstered by a blizzard of Internet blogs from outside his home state. His roster of visiting campaigners was uniformly of the same political slant – notably Jesse Jackson, Al Sharpton and Rep. Maxine Waters of California.

Now, with former Lieberman supporters such as Connecticut Sen. Chris Dodd and Rep. Rosa DeLauro closing ranks behind Lamont, the novice candidate will have an opportunity – and an urgent need – to moderate his stance and attempt to broaden his base.

DeLauro told me that Lamont has to be “more than an anti-war candidate,” and said that he has to balance his calls for an early withdrawal from Iraq with other positions that demonstrate that he and his party understand the need for a robust military and a commitment to oppose terrorism. With hopes of defeating not just Shays but also two other Connecticut Republicans, the Democrats simply cannot afford to be “McGovernized” by the GOP charge that they would abandon the fight against those who have targeted the United States.

Nonetheless, you can see the disillusionment with Iraq coloring Democratic politics more broadly. Hillary Clinton, that most cautious of centrists, delivered a public tongue-lashing to Don Rumsfeld last week over his mismanagement of the war and said he should resign. And New Mexico Gov. Bill Richardson, who is coordinating the party’s effort in the 36 gubernatorial races, told me this week that he thinks the Iraq issue “will spill over” into those contests, adding two or three points to the Democratic side. With American generals talking openly about Iraq verging on civil war, he said, “it allows Democrats to take positions that are responsive to the public and yet are protected from Republican political attacks.”

The opposition to current policy in Iraq is building – and so is dissatisfaction with a Washington that seems to be drowning in partisanship and incapable of breaking its policy gridlock on immigration, energy or health care. The protests are coming from both the right and left, but the greatest frustration is among the broad swath of centrist voters who feel they have no voice. In this environment, incumbents of neither party can feel safe.