President Barack Obama has a Democrat problem.

Despite signs of improved party unity on health care reform in the wake of his address to a joint session of Congress last week, Obama and Democratic leaders in the House and Senate are still struggling to persuade skeptical Conference moderates to support their reform plans.

The president’s apparent flexibility on the public insurance option does appear to have assuaged some centrist Democratic Senators on a key issue. But these Democrats remain resistant — particularly over the price tag, including how much reform will cost the government and what it will cost taxpayers.

“I want to make sure it’s not going to add 1 cent to the deficit. I want to really verify that with a close examination of the scoring,— said Sen. Ben Nelson (Neb.), one of several Democratic moderates who met with Obama the day after his address to Congress.

In fact, Obama implored the group of 17 mostly moderate Democratic Senators that he met with Thursday not to rely only on scoring from the nonpartisan Congressional Budget Office to determine whether his plan is deficit-neutral and adequately addresses the cost issue.

According to a Democratic Senate aide familiar with the White House gathering, the president attempted to sell the Senators on his proposals to lower health care costs and realize savings that might not be confirmed by a CBO score. For instance, the CBO has declined to score assumed savings from implementing wellness and prevention measures, arguing that such proposals cannot be empirically quantified.

“The president was trying to explain that his plan will have real savings in there over the long term, even though they may not be reflected in a CBO score,— this aide said.

Obama delivered the rare prime-time address to a Congress in the hopes of jump-starting health care reform efforts this year. The move came after an August recess in which Democrats came under fire at home for their reform plans.

In the Senate, negotiations continued last week in the Finance Committee, where a group of three Democrats and three Republicans, led by Chairman Max Baucus (D-Mont.) and ranking member Chuck Grassley (R-Iowa), has been attempting to reach a deal on a bipartisan health care bill. Baucus is expected to formally introduce legislation as early as Tuesday whether or not consensus is achieved, with bill markup to follow next week.

But even as movement in the Finance Committee puts the Senate one step closer to a floor vote and is sure to ease some of the frustrations felt by an impatient White House and Democratic leaders, the bloc of centrist Democrats continues to loom as a key obstacle.

“My feeling is, [health care reform] can’t just be paid for in a 10-year window. It has to be paid for in the out years as well. We’ve got to start driving the cost curve down,— Sen. Mark Warner (D-Va.) said. “This is so much bigger than health care. It goes to the deficit. It goes right to the heart of our competitiveness.—

Warner, a moderate former governor and one-time business executive who participated in the Thursday meeting with the president, said he believes the Obama administration understands this.

Most moderate Democrats appear to have responded positively to Obama’s speech, his latest move to recast the health care debate. They share his general philosophy of wanting to improve health care delivery, increase access to care and lower insurance premiums, which have risen sharply in recent years and are projected to continue in that direction.

However, the politics of any vote on health care reform legislation is being considered very seriously by moderates, particularly by those running for re-election next year in conservative-leaning states. Additionally their concerns about cost are legitimate and very real, the Democratic Senate aide said.

“Those who are in cycle will hold their powder until they see how some of this plays out — particularly because of how this August played out,— this aide said.

One senior Senate Democratic aide conceded that the devil is in the details for many moderates. And, Senate Democratic leaders are mindful that they need to massage the bill to satisfy them, but Majority Leader Harry Reid (D-Nev.) said Thursday that he does not believe moderates will derail passage of a bill.

Democratic leaders are confident that enough moderates will ultimately be on board so they can advance a bill by year’s end. Although the final shape of health care reform in the Senate remains unclear, the bill that Baucus is poised to drop in the Finance Committee is seen as a good model for what could attract significant moderate support.

A senior Democratic Senate aide said that while centrists may be some of the loudest complainers now, they are aware of the political perils of filibustering their own party’s health care bill.

“All posturing aside, we’re going to close ranks and we’re going to come together,— the aide said. “There isn’t a moderate out there on our side that wants to be known as the one who killed health care reform.—