Still, the turnabout since Jan. 20 — the first anniversary of Mr. Obama’s inauguration and the day after Scott Brown, a Republican, won a Senate seat in liberal Massachusetts — has been remarkable. Then, commentators pronounced the Obama presidency nearly dead. Today, he looks more like a liberal answer to Ronald Reagan.

“If you’d asked me about this administration after Scott Brown was elected, I’d have told you it was going to fizzle into virtually nothing,” said Theda Skocpol, the Harvard political scientist. “Now it could easily be one of the pivotal periods in domestic policy.” But, Ms. Skocpol added, “It will depend on what happens in the next two elections.”…

Will this new progressive project succeed? There are any number of uncertainties: whether enough charter schools will succeed, whether the new health insurance markets will function well, whether the Fed will learn to become an effective regulator of Wall Street.

Some of those questions won’t be resolved for years. But one issue should become clear much sooner. Mr. Reagan, Mr. Johnson and Franklin D. Roosevelt cemented their changes by retaining enough allies in Congress and serving more than four years in the White House. Mr. Obama has yet to do so.