But both Georgia Democrats pulled off upsets, putting Mr. Schumer in control of the Senate with the barest possible room to maneuver — a 50-50 margin, with Vice President Kamala Harris serving as tiebreaker. He said the weight of the task hit him as he scrolled through Georgia runoff returns in the early morning hours of Jan. 6.
“I realized the huge responsibility on the shoulders of our Democratic majority, narrow though it is,” Mr. Schumer said. Democrats needed to provide added pandemic relief and attack deep-seated problems such as racial injustice and climate change while restoring public faith in elections and government. Events later on Jan. 6 would add to the burden.
Despite the crush, Mr. Schumer and Democrats see themselves as having surpassed expectations with a broad $1.9 trillion pandemic relief bill already on the books, confirmation of the president’s cabinet with only one candidate withdrawn and an impeachment trial that drew Republican support for conviction of Donald J. Trump and met Democratic demands to hold him accountable for the assault on the Capitol.
“I never would have predicted this much success, simply because of my 10 years so far in the United States Senate, where we have been stymied at every turn by Republicans,” said Senator Richard Blumenthal, Democrat of Connecticut, who credited Mr. Schumer for focusing on achievable goals.
“I think we’ve shown real momentum,” Mr. Schumer said.
Republicans are not impressed, as shown by their icy response on Wednesday night to Mr. Biden’s push for his $2.3 trillion infrastructure plan — the G.O.P. proposal is $568 billion — and a new $1.8 trillion family assistance and education program. Senator Mitch McConnell, Republican of Kentucky and the majority leader, has ripped the infrastructure plan as a “sloppy liberal wish list.” He persistently accuses Democrats of overreach, a power grab and a steady drift toward socialism.
“The first 100 days have left much to be desired,” Mr. McConnell said Wednesday.
But Mr. Schumer’s calculation, which mirrors Mr. Biden’s, is that there is a disconnect between Washington Republicans typified by Mr. McConnell and Americans — even those who vote with the G.O.P. — who have seen the benefits of the Democratic agenda and would welcome more. Mr. Schumer said Democratic lawmakers have found that voters of both parties appreciate concrete results such as the multiple stimulus checks they have received to tide them over during the pandemic.