MIDDLETOWN, CONN. -- Sen. Joe Lieberman gets a bear hug from proprietor Brian O'Rourke when he stops by O'Rourke's Diner to schmooze with voters.

The welcome is less warm in the booth where Khachig Tololyan and Ellen Rooney are ordering lunch. Like Lieberman, the two college English professors are Democrats. But Rooney is dismayed by the senator's support for the Iraq war, Tololyan by "just a general sense that Lieberman is too often with the Republicans."

These days, elected officials who cross party lines -- a vanishing breed in today's polarized politics -- risk getting squashed.

Six years ago, Democrats lionized Lieberman as Al Gore's pitch-perfect running mate. In his Senate race in 2000, Lieberman won 63% of the vote and a third term almost without campaigning in the state. There's no free ride now: Businessman Ned Lamont says that next week he'll launch a primary challenge, inspired by Lieberman's stance on Iraq.

It's not just Lieberman, the most outspoken Democratic supporter of the war. In the state next door, Rhode Island Sen. Lincoln Chafee faces a challenge in the Republican primary from Cranston Mayor Stephen Laffey. Chafee was the only Senate Republican to oppose the Iraq war resolution, and the only one to vote against Samuel Alito's confirmation to the Supreme Court.

The primary challenges to the Senate's most liberal Republican and one of its more conservative Democrats are signs of the litmus tests that partisan voters on both sides are applying this year. They come as advocacy groups, including the conservative Club for Growth (backing Chafee's opponent) and the liberal MoveOn.org (which may support Lamont), are increasinwilling to help finance primary challenges to incumbents.

In Tuesday's primary in Texas, MoveOn.org is targeting Democratic Rep. Henry Cuellar because of his coziness with President Bush. (While MoveOn is raising money for challenger Ciro Rodriguez, the Club for Growth is doing the same for Cuellar.)

And in Ohio, Sen. Mike DeWine, up for re-election this year, is getting flak from fellow Republicans for joining the Gang of 14. A deal forged by the bipartisan group of senators thwarted Democrats from using a filibuster to block some controversial judicial nominations, but it also preserved the maneuver for "extraordinary" cases.

The bottom line: Voting records that once might have been seen as a sign of independent-minded statesmanship are now an invitation for an intraparty brawl. Strong feelings over the Iraq war in particular are sparking protests by anti-war Democrats toward elected officials who try to find some middle ground. Even New York Sen. Hillary Rodham Clinton, the party's most prominent liberal, has been criticized in her state for supporting the Iraq war resolution.

Such friendly fire "sends the message that you've got to toe the line," Lieberman says in an interview. "You've got to toe the line of party orthodoxy if you want to stay in office, and that's not where most Americans are."

Chafee agrees. "I don't think the American people want a Congress of robots that just knee-jerk obey their leadership," he says. "They want a Congress where there will be vigorous debate on the issues within the parties and between the parties."

At the diner, Lieberman slides into a booth for a teasing exchange with 4-year-old Skylar Vicino. He's hailed like an old friend by Katchen Coley, 81.

"There are Democrats who are upset at his stance on the war, but I tell them you've got to weigh your options," she says. "Nobody agrees with any of us on everything."

Coley strongly supports Lieberman.

She's a Republican, by the way. 

Friends and foes  

Lieberman's approval rating among fellow Democrats in the Nutmeg State is a middling 57%. Among Republicans, it's 71%, according to a Quinnipiac University survey last month.

That upside-down standing is shaped by views of the war, poll director Douglas Schwartz says. Lieberman was an early proponent of toppling Iraqi dictator Saddam Hussein, argued in a Wall Street Journal op-ed article in November against reducing U.S. troop levels in Iraq, and then warned critics about the risks of undermining Bush.

His stance has boosted him among Republicans but cost him Democratic support. Two-thirds of Connecticut Republicans in the survey said going to war was "the right thing to do," but eight of 10 Democrats said it was wrong.  

In Rhode Island, Chafee fares better among Democrats than he does with fellow Republicans. In a Brown University poll last month, most Democrats said they would vote for Chafee in the general election over either of two Democrats. Only about one-third of Republicans said they'd back him over either Democrat.

The senator's strategy to survive the Sept. 12 primary is to attract independent voters, who are eligible to participate in either party's contest. "I certainly am going to fight for every Republican vote," he says, "but I've got to make sure my supporters amongst the unaffiliated come into my primary."

At 52, he faces the toughest race of his career.

"Usually the formula for success for Republicans in Rhode Island has been to avoid a primary ... and have a raucous Democratic primary in which the combatants spend their money and bloody each other up with negative ads," Chafee says. That's what happened when he won the Senate seat on his own in 2000. He had been appointed to complete the term of his father, John, who died in 1999.

This time, however, negative ads on the Republican side already are on the air. TV spots for Chafee financed by the National Republican Senatorial Committee portray Laffey as a comic-book character starring in "Laffeyland Tales." Radio ads for Laffey paid for by the Club for Growth warn that Chafee "votes against the Republican Party more often than any other Republican."

There are few kind words about Chafee when the Lincoln Town Republican Committee gathers at the Enrico Caruso Club in Manville for its annual Lincoln Day Dinner. 

Charles Gauthier, 82, a retired supermarket manager, affectionately recalls Chafee's father, who won three terms as governor and four as senator. "The Chafee name is gold to me," Gauthier says.

Others at the table say the current senator is not his father's son, at least in politics. "He lost me a long time ago" by voting against Bush's tax cuts in 2001, says Marc Beausoleil, 46, a cutlery salesman. For Roger Gladu, 67, a retired mail carrier, the last straw was Chafee's vote against Alito.

They like what they hear when Laffey rises to speak.

"The Republican ideals that so often are being missed in this state are coming back," Laffey, 43, tells them. His heroes: Abraham Lincoln, Teddy Roosevelt and Ronald Reagan. His business background helped him straighten out city finances when he took over, he says, including a celebrated showdown with unionized school-crossing guards.

Chafee is soft-spoken and sometimes diffident; Laffey is blunt. "We go right to the people," he declares. "Make some people mad. Step on some toes."

He never mentions Chafee by name. The next day, though, the senator is depicted in a PowerPoint presentation that Laffey clicks through as he unveils his prescription-drug proposal. "Chafee" is a stick figure with a bow tie, lurking nervously along the edges.

In Connecticut, campaign paraphernalia needle Lieberman, too. A liberal website, www.dumpjoe.com, features a button with a photo of Bush kissing Lieberman after the State of the Union address in 2005.

"As I always point out," Lieberman demurs, "he kissed me." 

Less bipartisan bussing  

A Senate without Lieberman, Chafee and the few other senators who regularly break ranks with their party presumably would feature less bipartisan bussing and sharper ideological lines. It would be more difficult to forge centrist alliances such as the Gang of 14, which included both of them.

Already, the ranks of conservative Southern Democrats and liberal Northeastern Republicans have been "weeded out" of the Senate, says political scientist Morris Fiorina of Stanford. That makes thorny legislation such as the landmark 1983 compromise to rescue Social Security's finances much more difficult to reach. "It's why both parties have their feet stuck in the concrete right now on most of the issues," Fiorina says.

The Senate's most famous maverick, Republican John McCain of Arizona, has built credibility among independents by bucking party leaders. But even he has been mending his fences within the GOP -- campaigning for Bush's re-election in 2004, for instance -- as he prepares for a potential run for president in 2008.

For incumbents, there's often tension between the most partisan voters and everyone else, Fiorina says. Sometimes moderation that reflects the sentiments of the broad ranks of voters in general elections can upset the primary voters who decide nominations.

That's one reason Lieberman says he's taking his primary challenge seriously despite a 68%-13% lead over Lamont in the Quinnipiac survey. There are some warning signs: Just 52% of those in his own party said Lieberman should be renominated. And developments in Iraq before the Aug. 18 primary could stoke opposition to the war and questions about the senator's support of it.

He isn't backing off his stance on Iraq. "I truly believe it is best for the safety of our country," he says. But he takes pains to remind voters of his Democratic credentials on other issues, including the environment.

Lieberman, 64, hasn't faced a primary fight before, but he recalls his first Senate election against Republican incumbent Lowell Weicker.

"You might say that I got to be a U.S. senator because for the better part of an election year in 1988, the incumbent senator didn't take me seriously," Lieberman says. "I'm not going to make that mistake."

He has banked more than $4 million for the campaign and lined up key endorsements. Senate Democratic leader Harry Reid, who has criticized Lieberman on Iraq, says he's warned Lamont that he would campaign for the senator.

Lamont, 52, says he's serious, too. "On a hot day in early August, whoever can get people who feel passionately about the issues is going to win," he says in an interview.

He shows up promptly to make his pitch to the Southbury Town Democratic Committee. Democratic groups in Manchester and Windsor already have chastised Lieberman for supporting the war. The Southbury group is weighing whether to back Lamont.

The millionaire owner of a cable TV company in Greenwich, Lamont seems an unlikely insurgent. He sports a dark suit and an unflappable demeanor. His only previous political post was a local one, as a Greenwich selectman.

"Like a lot of you, I responded with a certain amount of pride when Al Gore asked Joe Lieberman to join him on the national ticket" in 2000, he says. "What a difference five or six years can make. It seems that Al Gore has really found his Democratic voice in that period of time, and Joe continues to lose his."

In the audience, Ken Kerin, 67, nods in agreement. "It's nice," he says, "to hear someone who sounds like a Democrat."