Centrist Democrats may be finally ready to flex their enhanced muscle in the Senate, but if they’re casting around for a point man to help them harness their power, they haven’t found one yet.

Sen. Tom Coburn (R-Okla.) is often mentioned as the de facto leader of the GOP’s rump caucus, and former Sen. John Breaux (D-La.) often played that role for Senate Democratic moderates until he retired from the chamber in 2005.

Now, with powerful forces attempting to push President Barack Obama and Congressional Democratic leaders to the left, Sens. Evan Bayh (Ind.) and Ben Nelson (Neb.) appear to be positioning themselves to try to become the new Breaux, who in his heyday acted as a broker who could bring others to the table with him.

While both men have been perhaps the most outspoken centrists about their desire to moderate the debate on health care, energy and other Obama initiatives, neither Bayh nor Nelson has yet proved to be the whole package that Breaux often represented — and it’s not clear that they want to be.

“First of all, I’m not competing to be the leader of any group,— Nelson insisted Wednesday. “What I’ve done is offer some ideas on health care and on energy. Leadership is established when people want to follow you. And so I guess the question will be whether anyone wants to follow what I’ve offered.—

For his part, Bayh also said he isn’t necessarily interested in always being the go-to guy for every deal with centrists, but he indicated that he hopes he has created a platform for both himself and others to become powerful voices in the major policy debates that are in the pipeline. Bayh created the Moderate Dems Working Group along with Sens. Tom Carper (D-Del.) and Blanche Lincoln (D-Ark.), but aides said he has done the yeoman’s work in keeping the nascent group afloat.

“I’m content to let Members who are particularly interested in an issue lead the way,— Bayh said. “Sometimes the most effective leadership is in letting other people lead the way. … I’m not going to insist on a leadership role at all times.—

Bayh joked that he may not be the best person to take over the role that Breaux did so well because “he’s a little bit more flamboyant than I am.—

But since Breaux left, centrist groups have come and gone, and the jury is still out on the Moderate Dems Working Group, which meets every other Tuesday to discuss upcoming policy debates.

Sen. Mary Landrieu (D-La.) said Senate centrists don’t have a leader because they don’t want one.

“The reason is, that’s kind of the way we like it,— she said. “We just sort of like to be, you know, a table of equals on this. And we are.—

Landrieu echoed Bayh’s assertion that different Members will step up at different times. She said that Sen. Joe Lieberman (ID-Conn.) sought to be a leading centrist years ago but that the moderates’ enhanced numbers after the 2006 and 2008 elections have made it more difficult to have one leader.

“Ten years ago, Joe Lieberman was kind of established — or established himself — as one of the original centrist voices. But now that our group has gotten quite large — I mean there are about 15 of us — there really is no leader,— she said.

Part of the problem, said one former Senate Democratic aide, is that there is a split among centrists over how to actually flex their power.

Bayh, for example, is more in the camp where the centrists’ “would be unionized within the party and collectively bargaining with the leadership,— the former aide said. Bayh acknowledged that centrists speaking with one voice could be useful, but he said he was not necessarily seeking to be their spokesman.

Nelson, however, appears to be more in the camp of moderates “who think of themselves as centrists first and centrist Democrats second,— the former aide noted.

Democratic operatives said that Bayh and Nelson are well-positioned to be the centrist dealmaker but that both have drawbacks.

“I don’t know the extent to which Sen. Nelson is angling to lead,— one Democratic strategist said. “I think he’s flexing his muscle. … Bayh is looking for a platform.—

Indeed, Bayh has toyed with running for president and was mentioned as a vice presidential prospect in 2008. But those ambitions could undercut his ability to be an effective Senate leader. Meanwhile, Nelson appears content at times to go his own way, even if that means being a voice in the wilderness on some issues.

One senior Senate Democratic aide noted that just because the two men have sought the spotlight, “I don’t think it necessarily makes them more effective.— As the two most vocal centrists, Bayh and Nelson have occasionally staked out positions that put them in the minority, even among moderate Democrats. They voted against the Democratic budget this year, complaining that it was too bloated. The only other Democrat to follow suit — Sen. Robert Byrd (W.Va.) — did so because of his objections to a procedural maneuver that Senate leaders decided to use.

Current and former Senate Democratic aides said Bayh’s relationship with the larger Democratic caucus and the leadership is more strained than Nelson’s, largely because Bayh has appeared to poke leaders in the eye when he opposes the party line. One example was a Wall Street Journal opinion piece that Bayh wrote during this year’s debate on the omnibus appropriations bill accusing his fellow Democrats of larding it up with pork-barrel spending.

But the Democratic strategist defended Bayh, saying that he agonizes over bucking his leadership.

Nelson, on the other hand, has seemed to bend over backward to keep his leaders looped in on what he is doing and why. For example, Nelson’s role in forcing his party and his president to cut $100 billion from the economic stimulus bill didn’t sit well with some Democrats, but he got enormous credit from Democratic leaders for helping to keep the three Republicans whom he was working with at the table. Without those GOP Senators, the massive bill would likely have fallen to a filibuster.

Nelson said he is trying his hand again at building a coalition on health care and is still engaged with a bipartisan group seeking to find a middle ground on energy policy.

If Bayh or Nelson don’t work out, Democrats said they see a rising centrist star on the horizon in Sen. Claire McCaskill (D-Mo.). They noted that she has a close relationship with Obama despite her refusal to walk lock step with the party, and her plain-spoken ways remind many of Breaux.

But others said Senate Majority Leader Harry Reid (D-Nev.) has an interest in keeping any future centrist leader at bay given the unpredictability that individual moderates already pose by themselves.

“To Reid’s credit, there isn’t a well-formed rump group because he’s kept the caucus together,— the strategist said.