(CNN) -- House Democrats wary of the Senate health care bill find themselves in a quandary.
Now that the Senate parliamentarian has made clear to Democrats that they won't be able to take the path they had considered to get a health care bill passed, they must ask themselves: If we vote for the Senate's bill, do we trust the senators to make the changes they say they will?
"If the House is going to do this, they are going to have to vote for the Senate bill, holding their nose and trusting that in fact they are going to go through this reconciliation process, and they are going to get the fixes that they are looking for to the legislation," said Cheryl Block, a professor of law and a budget policy expert at Washington University in St. Louis, Missouri.
Those "fixes" are a part of a package of changes to the Senate bill that President Obama proposed last month. The idea is for the House to pass the Senate bill, wait for Obama to sign it into law, and then vote separately on Obama's proposal.
The Senate no longer has the 60-seat supermajority it did when it passed its health care bill in December, so it would need to pass Obama's plan using the parliamentary shortcut known as reconciliation.
Reconciliation allows a measure to pass on a simple majority vote of 51, rather than the 60 needed to break a filibuster. The tactic is limited to budget-related bills.
The parliamentarian clarified last week that reconciliation can be used only on existing law, meaning lawmakers can't vote on the Senate plan and Obama's proposal together.
Should the House pass the Senate plan, there's no guarantee that Obama's proposals will survive.
Once reconciliation gets under way, "the Republicans have any number of opportunities where they can raise points of order from the floor arguing that certain pieces are extraneous or inappropriate or inconsistent with reconciliation instructions, and each one of these points of order is one that the parliamentarian is going to have to rule on," Block said.
But that puts Republicans in a tough spot, too. If Republicans block the reconciliation package, lawmakers would be left with the Senate bill, which received no support from Republicans, Block noted.
The parliamentarian's decision leaves open one other option: Democrats could try to tie the changes they want in the Senate health care bill to other laws currently on the books. But it's not clear if that is feasible, especially because some key issues in the health care bill are not found in existing laws, such as how to pay for reform.
The Democrats' health care plan is on the line, but so are their jobs, with every House member up for re-election this year.
Sen. Lamar Alexander, R-Tennessee, told CBS' "Face the Nation" that passing the current health care package would have major ramifications for Democrats.
"I think from the day this passes, if it should, there will be an instant spontaneous campaign to repeal it all across the country. It will define every Democratic congressional race in November. And it will be a political wipeout for the Democratic Party. That will be bad for the country, but it will change the leadership of the country," he said.
Obama declared last week that Congress "owes the American people a final up or down vote on health care reform," but House lawmakers have shied away from Obama's call to vote on the Senate bill by Thursday.
David Axelrod, Obama's senior adviser, said Sunday that the administration is optimistic about the outcome.
"Many on the other side of the aisle have decided that it would be a political victory for them if health insurance reform were defeated, so it's a struggle, but I believe we are moving in the right direction," he told CNN.
House Minority Leader John Boehner said House Speaker Nancy Pelosi doesn't have the votes to pass the Senate plan.
"If she had 216 votes, this bill would be long gone, and remember, they tried to do this in June and July of last year. If they had the votes then, it would be law. They tried to pass it in September, October, November, December, January, February, guess what? They don't have the votes," he said in an interview that aired Sunday on CNN's "State of the Union."
House Democrats' vote counter Rep. James Clyburn, the party whip from South Carolina, told CNN Monday he was "very comfortable" that the votes to pass the Senate bill in the House were there.
"I think we have reached a significant consensus in our caucus. The will is there to get this done," Clyburn said on CNN's "Campbell Brown."
All House Republicans oppose the Senate plan, as do a threatening number of Democrats.
Some House Democrats are wary of the Senate bill because its language on federal funding for insurance plans that cover abortions is less restrictive. They also oppose some of the exemptions in the Senate bill, such as a provision that exempts Nebraska from paying increased Medicaid expenses. The issue of illegal immigration, which is dealt with more strictly in the Senate bill, is also a sticking point in the House.
Obama's package of changes sits easier with House members. While it more closely resembles the Senate plan, it eliminates some of the provisions the House opposes.
John Feehery, who worked for former House Speaker Dennis Hastert and other Republicans in Congress, said House members are now asking themselves, "Can we trust the Senate?"
"If we pass their bill, will they pass ours? If we go out on a limb for them, will they change their Senate rules for us?" he wrote in a commentary on CNN.com.
"Well, as President Ronald Reagan used to say about the old Soviet Union: Trust. But verify. Which really means don't trust them at all," he said.
Asked if Obama can give any promises that the fixes will become law, White House press secretary Robert Gibbs, appearing on "Face the Nation," said, "Just as the president is speaking with members of the House about passing the underlying Senate bill, I know he's also talking to members of the Senate about making sure that the corrections that he believes have to be passed to the Senate bill are indeed taken up and passed."
The House Budget Committee officially started the reconciliation process Monday.
CNN's Lisa Desjardins contributed to this report.