This week, a loose federation of left-leaning groups is convening nearly 200 gatherings to peddle the virtues of health-care reform. A women’s speak-out in Philadelphia. A small-business round-table discussion in Albuquerque. A fish fry for seniors in Columbia, S.C. From the Obama administration alone, 42 officials are fanning out to events in 22 states.

The choreography coast to coast is a birthday party, of sorts, to mark the year that has elapsed since President Obama signed into law the broadest changes to the nation’s health-care system in nearly half a century. But the commemoration is as much a strategy for image-shaping as a reflection of the new reality on the ground.

A year after a titanic partisan battle in Congress yielded a 2,073-page statute, the law exists in what one seasoned health-care lobbyist called “a very weird place. It’s like we have two worlds.”

In one, federal officials are working at a fevered pace, writing regulations, planning innovations for the delivery of care, and giving states grants and guidance. That complex work is “even a little ahead” of expectations, said Urban Institute President Robert D. Reischauer, an authority on health-care policy.

In the other world, Reischauer said, the future “is very uncertain right now. . . . Today, I wouldn’t give much more than a 50-50 chance that all of the critical components of the Affordable Care Act will be alive and well . . . . Court decisions, defunding efforts or actual repeal of some major provisions could eviscerate the dreams of universal coverage and restrained cost growth.”

The administration is trying to focus attention on the parts of the law that have taken effect earliest, though the number of people helped so far is relatively small — or unknown.

For instance, nearly 12,500 Americans have joined high-risk pools that were created to cover people who were rejected by insurance companies because of medical problems. The enrollment so far is about 3 percent of government forecasts.

The White House is touting figures showing that nearly 4 million older Americans on Medicare with especially large prescription-drug expenses received $250 rebate checks last year, the first installment of a coverage gap that will be closed over several years. That is about one in eight people with the program’s drug benefit.

Other parts of the law that took effect last fall allowed young adults to remain on their parents’ insurance policies longer and have forbidden insurers to deny coverage to sick children. No one knows how many people either provision is helping.

In lieu of data, administration officials are spotlighting testimonials from people who have been helped — including in this week’s gatherings nationwide. Uwe E. Reinhardt, a health economist at Princeton University, said such anecdotes “have very powerful amplifying effects if they are powerfully told.”

One central test for the law will come in the 2012 elections: If Republicans win the White House or sweep Congress, “they can take this thing apart,” said Robert Laszewski, an analyst and consultant with clients across the health-care industry. Ethan Rome, executive director of Health Care for America Now, a grass-roots coalition supporting the law, said that undermining it has become a “near-psychotic obsession” for Republicans.

Next year, too, is when constitutional challenges to the law — focused mainly on its requirement that most Americans carry health insurance as of 2014 — may be settled by the Supreme Court. If the justices struck down the insurance mandate, health-care experts say, the Obama administration and congressional Democrats would almost certainly need to reopen the statute — creating, in turn, a legislative opportunity for its conservative critics. If the court upheld the mandate, on the other hand, the ruling could impart new legitimacy to the aspect of the law that has been least popular with the public.

Americans’ sentiment remains frozen essentially where it has been since before the debate in Congress began. According to monthly surveys by the Kaiser Family Foundation, a nonpartisan health policy and research organization, support for the law has never quite broken 50 percent. The dominant feeling about the legislation, the surveys show, is confusion — now reported by 53 percent, just two percentage points less than 11 months ago.

“Until people see it, smell it, touch it, feel it, they don’t really believe it,” said Joseph Antos, a scholar at the conservative American Enterprise Institute who opposes the law.

Against that backdrop of public uncertainty, proponents are using this week to highlight what they call the legislation’s benefits. “I’ve really been able to see firsthand how the new law is already helping Americans get the treatment and medicine they need,” Health and Human Services Secretary Kathleen Sebelius said in a conference call Tuesday with journalists and older Americans.

Regardless of whether support for the law grows, large unknowns hover over how the statute will work, if it reaches the key year of 2014 intact. According to health policy experts, they include:

- What kinds of care will be included in a package of “essential health benefits” that all health plans must provide in new insurance marketplaces, called “exchanges,” for people to buy coverage individually or through small groups? And how will that decision influence insurance rates?

- How much will the insurance sold through the exchanges cost and, even with new federal subsidies, will middle-class Americans be able to afford it?

- With states responsible for creating the exchanges, how many will use them aggressively, as a tool to lower costs and change the delivery of care?

- Will many healthy Americans decide they would prefer to pay a federal penalty rather than comply with the individual mandate?

- Will employers who offer insurance to their workers decide to drop the coverage, leaving people to find it through the exchanges — with the potential ripple effect of higher federal spending on the subsidies?

- And will the law slow the nation’s rampant spending on health care?

In the meantime, some insurers, hospitals and doctors are preparing for the legislation’s implementation. Others, Laszewski said, “are treading water,” reluctant to make big changes or to invest in expensive information technology until they are certain the law will remain intact.

That uncertainty is likely to linger until at least after the 2012 elections and — if Democrats retain enough power — the “guts of the law go into effect” in 2014, said Drew Altman, president of the Kaiser Family Foundation. “That’s when there will be a real verdict on the law. Now people are reacting to sound bites on TV, as opposed to direct experiences.”