In a move that could further imperil his already weakened status in the Democratic Caucus and fuel talk about his split loyalties, Sen. Joe Lieberman (ID-Conn.) Wednesday took center stage in the GOP’s mounting attacks on the presumptive Democratic presidential nominee, Sen. Barack Obama (Ill.).

Lieberman participated in a media conference call Wednesday morning organized by House Minority Chief Deputy Whip Eric Cantor (R-Va.) criticizing Obama’s stance on the Middle East.

Lieberman’s criticisms came in response to Obama’s speech before the American Israel Public Affairs Committee, which was his first major address after claiming his party’s nomination late Tuesday night.

Furthermore, during a Senate vote Wednesday, Obama dragged Lieberman by the hand to a far corner of the Senate chamber and engaged in what appeared to reporters in the gallery as an intense, three-minute conversation.

While it was unclear what the two were discussing, the body language suggested that Obama was trying to convince Lieberman of something and his stance appeared slightly intimidating.

Using forceful, but not angry, hand gestures, Obama literally backed up Lieberman against the wall, leaned in very close at times, and appeared to be trying to dominate the conversation, as the two talked over each other in a few instances.

Still, Obama and Lieberman seemed to be trying to keep the back-and-forth congenial as they both patted each other on the back during and after the exchange.

Afterwards, Obama smiled and pointed up at reporters peering over the edge of the press gallery for a better glimpse of their interaction.

Obama loyalists were quick to express their frustration with Lieberman’s decision and warned that if he continues to take a lead role in attacking Obama it could complicate his professional relationship with the Caucus.

“It’s a difficult situation,” Senate Majority Whip Dick Durbin (D-Ill.) said Wednesday. “Joe is my friend … but I hope he doesn’t become the lead attack dog.”

The longtime Obama supporter also acknowledged that Lieberman’s role in Sen. John McCain’s (R-Ariz.) presidential campaign continues to be a concern for members of the Democratic Caucus and could become more so if he continues to play such a prominent role in attacking McCain’s Democratic rival.

“Of course it’s a concern when someone in your Caucus is supporting the other party’s candidate. Let’s not try and sugarcoat it,” Durbin said.

While Lieberman Wednesday declined to say whether he would continue acting as a surrogate for McCain in attacking Obama, he stated that he would not put his work in Congress in jeopardy by participating in the McCain campaign.

“Obviously I support Sen. McCain … but I can only do so much as long as it doesn’t interfere with what I’m doing here,” Lieberman said.

When asked whether his activities should bring his role as chairman of the Senate Homeland Security and Governmental Affairs Committee into question, Lieberman said he would leave that decision up to the Democratic Caucus. “That’s up to my colleagues,” he said.

Lieberman’s status in the Democratic Caucus has been shaky since the once-vice presidential nominee left the party to become an Independent Democrat in 2006. The move was reinforced when Lieberman endorsed McCain for president and began actively campaigning and raising money on his behalf. Lieberman later said he would be willing to speak at the Republican National Convention in Minneapolis.

Senate Majority Leader Harry Reid (D-Nev.) has waded gingerly into the subject, given that the two Senators have long been personal friends. Three weeks ago during an interview with Keith Olbermann on MSNBC, however, Reid left open the possibility that Lieberman’s status as a committee chairman may not be secure indefinitely.

Reid, pointing out the Democrats’ narrow majority in the Senate and Lieberman’s support for the war in Iraq, said, “the facts are that we’re going to watch very closely.”

But Wednesday’s decision to proactively attack Obama may have taken things to a new level, Democratic Senators and aides said. Obama’s AIPAC speech was his first public policy address since accepting his status as the Democrats’ presidential pick Tuesday night.

A senior Democratic Senate aide said it remains unclear whether Lieberman has weakened his position further with his critique of Obama, adding that his status couldn’t get much worse after agreeing to speak at the GOP convention. “It’s all downhill after that,” the aide said.

But Lieberman loyalists such as Sen. Lindsey Graham (R-S.C.) say the Connecticut Senator’s posture shouldn’t be surprising given his unabashed support for McCain’s candidacy. Graham said Lieberman has shown the courage to put principles over politics, regardless of the consequences.

“I think it goes to the very approach of Joe Lieberman — he’s done something people in this body don’t do very often, which is risk your career,” Graham said.

Graham said that for Lieberman, it comes down to his steadfast belief that the war in Iraq must be won, and that the U.S. cannot leave open the door to any foreign enemy in the war on terror.

“I really do believe it’s appropriate for Lieberman to speak his mind, and he’s earned it,” Graham said. “Obama should listen to some of those criticisms. My feeling is Sen. Lieberman understands the war on terror is the defining issue of America. It means more to him than political alliances or friendships.”

Certainly, Lieberman has already raised eyebrows among his Democratic colleagues, wondering how he would handle himself once the general election rivalry had been set. Some have wondered privately whether Lieberman would continue to participate in Senate events and strategy sessions, especially since presidential politics are bound to come into play.

Sen. Sheldon Whitehouse (D-R.I.), while not familiar with Lieberman’s remarks at AIPAC, said there shouldn’t be a conflict as long as they doesn’t “interfere with his support or commitment to Democrats” on the floor and in terms of the agenda. “I think people around here get pretty good at separating politics from what we do here on the floor.”

Asked whether the dynamics have now changed since Lieberman clearly is weighing in against the Democrats’ presidential pick and fellow Senator, Whitehouse responded: “We’ve had some pretty big divisions with Sen. Lieberman already, and the way he’s conducted himself has kept him a valued Member of the Caucus.”