This really is the home stretch in the health care debate.

But after 199 laps around the racetrack, it is hard not to feel dizzy, and even a little lost. So here is a handy road map for the next three weeks — a sort of GPS guide to the health care finish line.

House Call

After all the frenzy last year about whether there would be 60 votes in the Senate, the main action is now in the House, where some Democrats are eyeing March 18 as a target for a vote.

Win McNamee/Getty Images Senator Mitch McConnell will lead opposition in the Senate.

To prevent a Republican filibuster in the Senate, Democrats are planning to include the final revisions to the health care bill in a budget reconciliation measure, which can be adopted by a simple majority in both chambers.

But first, House Democrats must approve the Senate’s health care bill, originally adopted Dec. 24. This is where the legislative heavy lifting will take place.

Many rank-and-file House Democrats are deeply uneasy. They disliked the Senate bill on both policy and political grounds. On policy, for example, many opposed the Senate’s proposed tax on high-cost, employer-sponsored insurance policies. Politically, they objected to several provisions included to win over individual senators, like extra Medicaid money for Nebraska.

President Obama has put forward a compromise plan, and this week the White House and Congressional leaders will continue working to resolve any remaining differences. Those changes, like eliminating the Nebraska provision, would be in the reconciliation bill.

The Magic Numbers

Confused about how many votes it will take to pass the Senate bill, and then the reconciliation bill, in the House? Even House Democratic leaders have been left guessing in recent days. The short answer is a simple majority present and voting. With a full 435 House members, that number is 218.

But there will not be 435. After a death and three resignations, including that of Representative Eric Massa, Democrat of New York, on Monday, there will be 431 House members. With everyone voting, 216 wins.

The number has changed several times. Representative Nathan Deal, Republican of Georgia, was set to resign to focus on running for governor, but is staying to vote against the health bill. Mr. Massa had opposed the bill, so his departure helps Democrats on the health care front.

The original House bill was adopted Nov. 7 by a vote of 220 to 215, with one Republican in favor and 39 Democrats opposed.

Representative Anh Cao of Louisiana, the lone Republican to vote yes, now says he will vote no. Some Democrats who supported the bill only because it had tight restrictions on insurance coverage for abortions are also wavering. Absent a deal on the abortion issue, Speaker Nancy Pelosi will need to persuade some Democrats who voted no in November to vote yes now. She believes she can.

Kathleen Sebelius, the secretary of health and human services, said Sunday that “there are lots of Republican ideas in the bill,” but it was unclear whether that would translate into any Republican votes. “We are hopeful,” she said on the NBC program “Meet the Press.” “But I’m not sure there will be.”

The Final Product

What is in the final version of the health care bill? Mr. Obama has offered an 11-page outline of how he would meld the House and Senate bills, and has also cited four issues raised by Republicans that he wants to address. But lawmakers have not seen legislative language, and the Congressional Budget Office has not issued a cost analysis.

The bill is expected to cost taxpayers about $950 billion over 10 years, with the expense more than offset by new taxes and cuts in federal spending, particularly on Medicare, so that the legislation would reduce future deficits by more than $100 billion by 2019.

The bill would require most Americans to obtain insurance, and would provide subsidies to help moderate-income people.

It would add about 15 million people to the Medicaid rolls, and over all is projected to reduce the number of uninsured by more than 30 million over 10 years.

It would tighten regulation of insurers, banning the denial of coverage based on pre-existing conditions, for instance.

It would impose the new tax on high-cost employer-sponsored policies, and would increase the Medicare payroll tax for individuals earning more than $200,000 and couples earning more than $250,000. And it would slow the growth in spending on Medicare.

The End Game

This week, Mr. Obama will begin making what White House officials are calling the “closing arguments,” focusing on steep increases in insurance premiums and his insistence that a comprehensive overhaul is needed rather than the incremental approach Republicans are demanding. Mr. Obama’s final push will include visits to Philadelphia on Monday and St. Louis on Wednesday.

Senate Democrats, meanwhile, are preparing for a procedural fight with Republicans over the reconciliation measure. The rules require provisions to focus on meeting budget targets, and policy changes with only an “incidental” fiscal impact will be struck out.

(This is why Democrats cannot make changes to the abortion provisions, and may need a third bill to resolve that issue.)

Democrats will go to the floor with a package they believe can pass muster with the Senate parliamentarian, aiming to complete it by March 26. Surprises are possible, and while debate on a reconciliation bill is limited to 20 hours, Republicans can offer unlimited amendments, which will mean politically charged votes intended to inflict damage ahead of the midterm elections.

Senate Democrats control 59 votes, so passage of the reconciliation measure is expected — especially with Senator Robert C. Byrd, Democrat of West Virginia, a legendary protector of Senate rules, supporting the process.Even a 50-50 tie would pass it, because Vice President Joseph R. Biden Jr. is the tiebreaker.

Still, some House Democrats want assurances — perhaps a letter signed by 50 senators — but they may have to rely on Mr. Obama’s word.

Democratic leaders want lawmakers to make a simple calculation: vote yes and chalk up an accomplishment, or vote no and be painted as a failure. “You have got the pain, now get the gain,” is one new mantra.

Republicans say they will use the health care bill as a weapon in the fall elections. “Just looking at the politics,” the Senate Republican leader, Mitch McConnell of Kentucky, said Sunday on the ABC program “This Week,” “there’s nothing but pain here for the next four years.”