For Maine Sen. Olympia Snowe, one really is the loneliest number.

Out of a total 217 Republicans in both chambers, Snowe is the only one to have actually voted for a Democratic health care proposal, but she cast her vote in the Senate Finance Committee on Tuesday with a strong caveat: “My vote today is my vote today. It doesn’t forecast what my vote will be tomorrow.—

But Senate Democratic leaders will surely be working to maintain her support throughout the process. Snowe’s backing — she joined 13 Democrats in voting for the Finance measure — gives them fresh leverage with their own fence-sitting moderates as well as the ability to call the bill bipartisan.

“This is what a profile in courage looks like,— one senior Senate Democratic aide said. “There may be a couple or so other Republicans who end up voting for the bill on the floor, but very few of them would have had the guts to be the first.—

The aide added, “Health care reform didn’t just gain one Republican vote today, it gained about four or five centrist Democratic votes. Snowe’s support, assuming it holds, will provide the cover many moderates needed to vote for this bill.—

Indeed, Snowe is likely to be a frequent visitor in the office of Senate Majority Leader Harry Reid (D-Nev.) as he begins to sit down with White House officials, Finance Chairman Max Baucus (D-Mont.) and Sen. Chris Dodd (D-Conn.) to merge the Finance bill with a more liberal measure that Dodd shepherded through the Health, Education, Labor and Pensions panel. The first meeting is expected today, though not necessarily with Snowe in attendance.

Reid spokesman Jim Manley said Snowe’s support is important, but is just one vote among many that Reid will need to shore up before the Senate completes its work.

“Today’s action was very important to the process,— said Manley. “In light of the fact that we’re looking at a Republican filibuster, every vote is important.—

He added, “Sen. Reid expects to work closely with her.—

Other sources said Snowe herself will determine her own involvement.

One senior Democratic source said Reid and the White House would have to feel out how much she will give on issues such as a public insurance option and the overall price tag of the bill. The Finance bill has been scored at $829 billion, whereas the other Democratic health plans have come in at more than $1 trillion.

“Early on, you have to sit down with her to figure out what her goals are and what the tolerance levels are,— the source said.

The senior Senate Democratic aide, however, said: “The crux of her remaining concerns relate to affordability … which is an issue most Democrats care about, too. Holding onto her won’t be as hard as people think.—

But Snowe on Tuesday shot down one option Democrats have said has promise — Sen. Tom Carper’s (D-Del.) proposal to allow states to create their own public insurance options.

Instead, Snowe said the “only [option] I can think of— is her own proposition to set a “trigger— or “safety net— for the public insurance plan in which it would kick in only if private insurers cannot reduce costs and increase coverage on their own. President Barack Obama, who has regularly spoken with Snowe during the health care debate, and Reid have expressed interest in the trigger proposal.

Still, it doesn’t appear that Snowe engaged in horse-trading with Senate Democrats for her Finance vote, a game that is often played in the halls of the Capitol to coerce people to take a stance that isolates them from their party. Reid, by all accounts, has not yet decided whether to include a trigger for the public insurance option, a public option that starts immediately, or some other proposal.

Last week, Snowe mocked the pundits for trying to project which vote would give her the most influence over the process.

“They’ve got me voting ‘yes’ preserving my leverage, voting ‘no’ preserving my leverage. It’s all about what I’m comfortable doing at the end of the day,— Snowe said.

Asked Tuesday whether she had solved the question of whether voting ‘aye’ or ‘nay’ gave her more power, Snowe said, “No, I didn’t actually. That’s a very good question. It’s sort of like 50-50 to be honest with you, but I thought it was important to just focus on the issue and … what I felt was the right thing to do at this moment.—

One former Senate aide said Snowe is not the type to engage in the typical political horse trade.

“She was clearly torn by this bill and probably felt that through a careful analysis that trying to move the ball forward was the better approach,— the aide said. “Her calculus must have included the sentiment that being a part of the process was more advantageous than saying ‘no.’ She believes that this way she might have the opportunity to ensure the bill doesn’t move to the left.—

Ultimately, Snowe said the bill may not be perfect but that “the consequences of inaction dictate— Congressional action, and she praised Baucus for exploring bipartisan compromise for months within the Finance panel’s gang of six, in which she was one of three Republicans. The other two — Finance ranking member Chuck Grassley (Iowa) and Sen. Mike Enzi (Wyo.) — declined to support the bill when it was unveiled and sided against it Tuesday along with every other panel Republican, except Snowe.

Snowe told reporters that her decision to support the bill “evolved— and that she was somewhat undecided when she entered the committee room Tuesday. But she said she firmed up her decision to support it after her questions were answered during the markup by Congressional Budget Office Director Douglas Elmendorf.

“I worked over the weekend on it,— she said. “I went back and forth there — I did — because it’s not an easy question. As you know, we’re so divided here between our Republican and Democratic colleagues.—

That understatement about the partisan divide in Congress belies the pressure Snowe has been under from her own party to reject any Democratic health care plan.

Asked last week whether it was fair to say that Minority Leader Mitch McConnell (R-Ky.) and other party leaders had asked her to oppose the Finance bill, Snowe responded, “I think it’s no secret about their preferences. We’ve had many conversations.—

Her GOP colleagues, she said, have made their feelings clear, albeit through gentle ribbing.

“You know, I think they understand the situation, you know, of where I am on this issue. I get some kidding about it,— Snowe said last week.

As for being the loneliest Republican in Congress right now, Snowe acknowledged as much Tuesday, but she said she hopes — as the Democrats do as well — that more Republican votes are out there.

“Yeah, that’s that way at this point in time, but I just need to say that can change,— Snowe said.