In retrospect, in the quest to win Republican backing for both, Democrats say, they settled for too small an economic stimulus and extended talks on the health care measure for too long. Those experiences explain why the White House and top Democrats are determined to move quickly this time on a plan for pandemic aid, and why they are reluctant to pare back their nearly $2 trillion stimulus package or make significant changes that would dilute it with no certainty of bringing Republicans on board.

“The dangers of undershooting our response are far greater than overshooting,” said Senator Chuck Schumer, Democrat of New York and the new majority leader. “We should have learned the lesson of 2008 and 2009, when Congress was too timid and constrained in its response to the financial crisis.”…

This time, Democrats say the new aid must be robust and delivered quickly. They do not intend to allow Republicans to dictate the timing nor the reach of the legislation.

“I’m not going to let Republican senators stall for the sole purpose of stalling,” Senator Ron Wyden of Oregon, the incoming Democratic chairman of the Senate Finance Committee, said on a conference call hosted by the advocacy group Invest in America. He added that his view grew out of his own experience serving as a junior member of the panel during the Great Recession.