The most important member of Congress this month may be a man you've never heard of: Jason Altmire, a painfully earnest former hospital executive from near Pittsburgh.

Why? Because as Jason Altmire goes, so goes the nation — at least when it comes to the Democrats' quest for health care reform.

Altmire, 41, is a centrist "Blue Dog" Democrat — a fiscal conservative who opposes big spending and higher taxes. His Republican-leaning district voted for John McCain in 2008 even as it sent Altmire back to Congress for his second term.

In November, Altmire was one of 39 Democrats who voted against his party's health care bill in the House. The bill squeaked through without his vote, 220 to 215.

But now the House is being asked to pass the Senate's health care bill, which is a bit more conservative than the House bill. And this time, unlike last year, President Obama and House Speaker Nancy Pelosi need Altmire.

Some of the Democrats who voted for health care last year, spooked by growing opposition, are likely to vote no this time. So to win, Obama and Pelosi need to move some of last year's no votes into the yes column, and Altmire is a prime target.

Altmire says he is torn. He wants Congress to pass a health care bill, mostly to give the government ways to help control the cost of medical care. But most of his constituents are skeptical that an Obama health care bill will be fiscally responsible. A Republican polling firm reported last week that voters in Altmire's district oppose the Senate bill 58 percent to 30 percent. He has been identified as a vulnerable Democrat who could be defeated this year, and a vote for health care reform could make him an even bigger target.

"If I vote yes, I know that would attract (unwanted) attention from across the country," he told me last week. "But health care is important to me. In the end, it's a choice between doing nothing and passing a bill that I have problems with."

At this point, the Senate bill isn't good enough to vote yes on, Altmire said. "About half of it I like; about half of it I don't." But if House-Senate negotiations produce fixes, including stronger cost controls, he could be persuaded.

Altmire, an expert on health care thanks to his earlier job as a hospital executive, is carrying on a conversation with his constituents through town meetings and television appearances.

"I know health care; I care about it," he said. "I feel I have an obligation to articulate the arguments."

Last week, he met with 46 "tea party" activists from his district who boarded a chartered bus at 5:30 a.m. for a chance to confront him in a House committee room.

Altmire gamely tried to convince his visitors that the Senate bill was better than the House bill. "You said don't do the 'public option,'" he said. "You said don't do an income tax increase. Your voice was heard. You won. Those things aren't in the bill."

But the tea party folks weren't impressed. "If you have 12 bad apples in a basket and you take three out, you still have nine bad ones," Charles W. Robinson, an attorney from Middlesex Township, retorted.

But the conversation ran aground when he asked a fundamental question: Shouldn't the government help low-income people afford basic health insurance?

"No!" most of the visitors shouted.

The tea party group, he knew, didn't fully reflect his district; many of them hadn't voted for him before and weren't likely to now. But he also knew that the Obama health care plan is a tough sell when his constituents are more worried about federal spending and the economy than they are about health coverage for the nation's uninsured.

Despite the polls, he said he thinks his district is "evenly divided" on the health care issue, although "there's more passion on the opposition side."

Obama's proposals have been misunderstood by many, he said. "When you talk about socialism or a government takeover, it's really hard to look at the bill and see that."

But it's not likely that those misimpressions can be corrected by the time Altmire runs for reelection this fall. So he faces a hard choice: Vote for an unpopular bill that he doesn't really love and risk his seat; or vote against it and miss the best chance in a generation to start reforming health care.

Altmire would clearly like to vote for a health care bill — one that includes real cost containment, doesn't increase the deficit and doesn't allow federal funds to subsidize abortions.

Two weeks ago, Pelosi suggested that members should be willing to risk their jobs in the cause of expanding health care coverage. "We're not here just to self-perpetuate our service in Congress," she told an interviewer.

Easy for her to say; Pelosi represents San Francisco, not conservative western Pennsylvania.

Altmire acknowledged that he worries about losing his job — but he agreed that keeping his seat wasn't the most important goal. "I'm here to represent my constituents," he said. "Their views are the most important thing."