With President Barack Obama poised today to roll out his final strategy for passing health care reform, House and Senate Democrats are scrambling to put the finishing touches on their endgame, trying to make sure the stars align perfectly for what is likely their only shot at passing an overhaul this year.

“We need to do everything right,” one senior Senate Democratic aide said. “Things have been plodding ahead, but the final decisions on an exact process, timing and substance still have to be made.”

Indeed, Democrats cannot afford to make any missteps on their road to final passage for a health care bill, even as they press for passage before the Easter break that begins in a scant four weeks, aides acknowledged. The process they have tentatively agreed to involves three separate and difficult votes: House approval of the $871 billion Senate-passed bill, and House and Senate approval of a precooked budget reconciliation bill that addresses House complaints about the Senate measure.

Obama’s speech today is intended to provide some momentum for that plan, given that he is set to outline his own proposal and how he wants Congress to pass it. White House officials said to expect the president to unveil a “broad outline” of his roughly $950 billion final blueprint.

But the president also faces one crucial task: instilling confidence in skeptical House Democrats that their initial support for the Senate bill — the basis for his plan — is a necessary means to enacting crucial reforms.

Obama also hinted in a Tuesday letter to Congressional leaders that his speech will reaffirm his commitment to a comprehensive plan and highlight specific GOP ideas that he is open to including in his final proposal.

Senate Majority Leader Harry Reid (D-Nev.) indicated the president’s newest bipartisan offerings would get serious consideration in the as-yet-unwritten reconciliation bill. Reconciliation allows the Senate to pass certain aspects of a health care overhaul with just 51 votes.

“After the President lays out a path forward in greater detail tomorrow, we should focus on putting those ideas into action and delivering reform to our broken health system this year,” Reid said in a statement.

Meanwhile, Speaker Nancy Pelosi (D-Calif.) made a major concession, signaling Tuesday that she may be ready to accept the Senate’s language on two issues that have divided her Caucus — immigration and abortion — in the name of getting an overhaul passed. Neither issue can be addressed under a reconciliation bill because stringent rules governing such bills require provisions to have a direct budgetary impact.

“This is not an immigration bill. It is not an abortion bill. It is a bill about affordable health care for all Americans,” she said.

However, leaders in both chambers are still negotiating what would be included in a reconciliation package and cannot secure the votes for any deal until they reach an agreement. Democratic leaders were mum Tuesday when they emerged from a bicameral leadership meeting with White House Chief of Staff Rahm Emanuel and health care adviser Nancy-Ann DeParle.

“It was a very good discussion,” Emanuel said afterward. “We worked through a number of issues as it relates to the legislation.”

Pelosi said she remains focused on finalizing the substance of a bill and figuring out what the Senate can pass. From there, House Democratic leaders “will take that substance … to our Members,” she said.

A senior House Democratic aide said party leaders aren’t whipping their Members until they have an actual bill on the table. Not that they haven’t already taken steps to bring more Democrats on board with Obama’s plan, whether it be by endorsing key provisions in his proposal or taking part in last week’s bipartisan health care summit.

“We’re not doing this in a vacuum here,” the aide said. “We’re creating an environment where people can get to ‘yes.'”

A cluster of largely retiring and freshman Democrats has emerged as a target of any future leadership whip effort; each voted “no” on the $1.2 trillion House bill that passed last fall and each is undecided on a final bill. They include Reps. Brian Baird (Wash.), Bart Gordon (Tenn.), John Tanner (Tenn.), Suzanne Kosmas (Fla.), Frank Kratovil (Md.), Scott Murphy (N.Y.), Glenn Nye (Va.), Michael McMahon (N.Y.) and Rick Boucher (Va.).

House Majority Leader Steny Hoyer (D-Md.) was optimistic Tuesday that some would flip their votes.

“Do I think there’s a possibility of some people changing? Yes I do,” he said. “That’s because it will be a different bill than either the House or the Senate bill. Hopefully, it takes the strengths of both. And I think that if that happens … Members look at it somewhat differently.”

Nor are Senate Democratic leaders whipping their Members yet, according to Senators and knowledgeable aides. Even liberals who have been agitating for passage of health care reform said their votes should not be considered a given until they see what is in the reconciliation bill.

“I need to be confident that I know exactly what it is that I’m signing off on,” Sen. Sheldon Whitehouse (D-R.I.) said.

Majority Whip Dick Durbin (D-Ill.) shed little light on when a bill would be ready for Senators’ perusal.

“I think it’s going to be very soon,” he said Tuesday. But Durbin said he has not begun “specifically” whipping because “we don’t have the reconciliation bill in its entirety.”

But several Senators said that once they see the bill, they would be willing to pledge their support in order to assuage the fears of House Members who fear the Senate would not be able to pass the measure if the House acted first.

“The House rightly needs to feel confident that we will support the changes that have been agreed to. I’m confident that we will be able to do that,” Sen. Debbie Stabenow (D-Mich.) said.

Emanuel indicated Tuesday that the House would have to pass the Senate bill before reconciliation measure could advance, saying that before that reconciliation package is brought up, “the bill would be dealt with in the House. The Senate bill would be dealt with.”

Still, Hoyer outlined a path forward for passing health care legislation that wouldn’t require House Democrats to first swallow a Senate plan many oppose.

While the House is required to initiate reconciliation bills, Hoyer said that doesn’t mean the House has to pass the Senate bill before passing a reconciliation package to amend it.

However, he said the president would have to sign the Senate bill before the reconciliation package.

But, perhaps complicating matters further, another senior Senate Democratic aide said the Senate Parliamentarian has already told leaders that a reconciliation bill must amend a law, not a bill that has not yet been signed by the president.