WASHINGTON — With the government reopened and a debt default averted for now, Congressional negotiators on Thursday plunged into difficult budget talks to avoid a repeat crisis within months, and quickly agreed to lower their sights from the sort of grand bargain that has eluded the two parties for three years.

After approval late Wednesday of the agreement ending the standoff, the deal-making mantle shifted overnight from the leaders of the Senate to the Budget Committee leaders, Senator Patty Murray, Democrat of Washington, and Representative Paul D. Ryan, Republican of Wisconsin, two less senior lawmakers who nonetheless could make very effective salespeople since they command loyal followings in their parties. The political pressure lifted as well, for now.

But the need for a bipartisan breakthrough, even a modest one, was amplified by the economic costs wrought by the 16-day shutdown and near-default on government obligations.

“The key now is a budget that cuts out the things that we don’t need, closes corporate tax loopholes that don’t help create jobs, and frees up resources for the things that do help us grow — like education and infrastructure and research,” President Obama said Thursday from the White House, setting ambitious goals for Congress even as his own role in the bargaining was unclear.