Washington ? It was a day of history for the nation — and sweet vindication for President Barack Obama. His grin seemed wider than any in recent memory.

After more than a year of arguing, struggling and dealing, Obama signed into law a nearly $1 trillion health care overhaul that ranks among the biggest changes ever devised by Washington and will reshape the way virtually every American receives and pays for treatment. It will rework fully one-sixth of the U.S. economy and for the first time cement insurance coverage as the right of every U.S. citizen.

At the White House, jubilation was in the air on Tuesday. Democratic lawmakers and advocates, crowded into the East Room for the signing ceremony, hooted and hollered at nearly every Obama sentence. They snapped photos of the president — and themselves. Vice President Joe Biden was caught whispering a profanity as he exclaimed to the president what a big deal it was.

It seemed more like a campaign rally than a bill signing. No one seemed quite able to contain themselves.

It will be months before the November elections render a verdict on whether the public approves of the bill the Democrats pushed through Congress without a single Republican vote. But after more than a year of hyperpartisan struggle — and numerous near-death moments for the measure — they sealed a victory denied to a line of presidents and Congresses stretching back more than a half-century.

Not everyone was cheering. Republicans said those Democratic lawmakers would pay dearly in this November’s elections. Opinion polls show the public remains skeptical, too, and Obama will fly to Iowa on Thursday for the first of a number of appearances that will be more like a continuing sales job than a victory lap.

Aside from the huge, real-life changes in store for many Americans, the White House hopes the victory — even as a companion Senate “fix-it” bill moves through the Senate — will revitalize an Obama presidency that has been all but preoccupied with health care for his first year and two months in office.

Republicans characterize the measure as a costly, wrongheaded government power grab. Obama and the Democrats portray it as literally a lifesaver for countless Americans.

The core of the massive law is the extension of health care coverage to 32 million who now lack it, a goal to be achieved through a complex cocktail of new mandates for individuals and employers, subsidies for people who can’t afford to buy coverage on their own, consumer-friendly rules clamped on insurers, tax breaks, and marketplaces to shop for health plans.