The United States economy showed signs of kicking into gear in March, adding 216,000 jobs and prompting President Obama to proclaim a corner finally turned.

The president and his fellow Democrats pointed to the latest jobs report on Friday, and to an unemployment rate that fell a touch to 8.8 percent, as evidence that their policies, like stimulus spending and the payroll tax cut, were working. All of this, they made clear, could become ammunition in their showdown with House Republicans, who have spoken of cutting deeply into the federal budget and have threatened a government shutdown.

An emboldened Mr. Obama spoke of the political implications before several hundred workers at a United Parcel Service shipping center in Landover, Md.

“If these budget negotiations break down, we could end up having to shut down the government, just at a time when the economy is starting to recover,” Mr. Obama told the workers. “So given the encouraging news we received today on jobs, it would be the height of irresponsibility to halt our economic momentum because of the same old Washington politics.”