WASHINGTON — In their first major test of governing this year, Republicans stumbled, faltered — and nearly shut down the Department of Homeland Security.

And that vote may have been the easy one.

In April, physicians who treat Medicare patients face a drastic cut in pay. In May, the Highway Trust Fund runs dry. In June, the charter for the federal Export-Import Bank ceases to exist. Then in October, across-the-board spending cuts return, the government runs out of money — and the Treasury bumps up against its borrowing limit.

All will require congressional action, and while many of these measures used to be pushed through in an almost unthinking bipartisan ritual, there is no such thing as simple in Congress anymore.

“We really don’t have 218 votes to determine a bathroom break over here on our side,” said Representative Charlie Dent, a Pennsylvania Republican. “So how are we going to get 218 votes on transportation, or trade, or whatever the issue? We might as well face the political reality of our circumstances and then act accordingly.”