In a July 14 New York Times article, reporter Mark Leibovich asserted that Sen. Joseph I. Lieberman (CT), “a self-styled 'independent Democrat,' ” “has not ruled out switching parties but has stopped short of saying he has moved so far from the Democratic Party -- or, in his view, the other way around -- that he is at a point of no return.” But Leibovich did not note that if Lieberman joined the Republican Party, he would, as Greg Sargent documented on Talking Points Memo, be breaking his promise during the 2006 campaign to caucus with the Democrats if re-elected to the Senate, a promise Leibovich himself has previously reported.

In a November 15, 2006, article, Leibovich reported: “During the campaign, Mr. Lieberman said repeatedly that he would continue to vote with the Democratic caucus.” Indeed, in October 2006, after Lieberman lost the Connecticut Democratic Senate primary to challenger Ned Lamont and decided to run for his seat as an independent, blogger spazeboy posted a video in which Lieberman was asked: “Would you unequivocally ... caucus with the Democrats?” Lieberman responded: “I've said that 1,200 times.” When asked to clarify with a “yes or no” answer, Lieberman responded: “Yes. Yes.”

In January 2007, Lieberman reportedly “asked to be called an Independent Democrat,” and “his office made clear that, if the compound modifier that the senator prefers was not going to take hold, then Lieberman's second choice is to be described as an Independent.”

From the July 14 New York Times article, headlined “Lieberman Finds Middle a Tricky Path”:

It has grown increasingly so for Mr. Lieberman, once his party's vice-presidential candidate and now a self-styled “independent Democrat.” He has zigzagged the country on behalf of Mr. McCain, the presumptive Republican presidential nominee, and, in recent weeks, amplified his criticism of Senator Barack Obama to a point that has infuriated many of his Democratic colleagues.

At least two have asked Mr. Lieberman to tone down his rhetoric against Mr. Obama, the presumptive Democratic nominee, two colleagues said, and at least three have advised Mr. Lieberman against speaking at the Republican convention, a prospect he has said he would entertain.

Clearly, Mr. Lieberman's already precarious marriage with the Democrats has reached a new level of discord and could be approaching divorce, if not necessarily a remarriage into the Republican Party. The strain has been rooted largely in Mr. Lieberman's steadfast support for the Bush administration's engagement in Iraq and his hawkish views on Iran. He has not ruled out switching parties but has stopped short of saying he has moved so far from the Democratic Party -- or, in his view, the other way around -- that he is at a point of no return.

“I don't have any line that I have in my mind,” Mr. Lieberman said in an interview. “If it happened, I'd know it when I saw it.”

Mr. Lieberman was leaning back in a chair in his Senate office, wearing a loose-fitting pinstriped suit, grinning a lot and appearing quite comfortable while describing “my uncomfortable position.” He compared his predicament to the old Groucho Marx conceit, “I don't care to belong to any club that will accept me as a member.”

[...]

He added that he was having a blast with Mr. McCain on the campaign trail, accompanying him on a trip to Colombia and Mexico this month. He has been a regular on Mr. McCain's Three Amigos circuit, which includes Senator Lindsey Graham, Republican of South Carolina.

All of which has angered his Democratic friends, or former friends.

“I think there's a difference in the way Joe has been treated now by people in his caucus compared to the beginning of last year,” Ms. [Susan] Collins [Republican senator from Maine] said. That was when Mr. Lieberman returned to the Senate after losing the Connecticut Democratic primary, running as an “independent Democrat” and prevailing in the general election.

Mr. Lieberman continued to vote with his party most of the time, while the Democrats, clinging to a 51-to-49 majority, smiled tightly and tried to hold on to their flight-risk colleague.

It has been tough, though. Mr. Lieberman has declared himself “liberated” from the shackles of party affiliation and seemed to delight in bucking Democrats on foreign policy matters. “There were times in my career where I really wanted to be supported, dare I say liked, by everyone,” Mr. Lieberman said in the interview.