Now that Democrats have defeated a major plank of the Republican agenda, the question is whether that success will drive President Trump and the Republican leadership to the negotiating table — and whether Mr. Schumer can keep Democrats who are up for election in red states in line and safe from defeat next year.
While Republicans have spent the last six months enmeshed in internal squabbling, Mr. Schumer has largely made sure Democrats stood on the sidelines. Mr. McConnell cut out Democrats on Day 1 of this Congress, using every method to bypass them on deregulation votes, cabinet confirmations, a tax overhaul and health care policy.
“That has had a big impact,” said Senator Dianne Feinstein, Democrat of California. “If you leave out a whole political party,” she said, “and then you chasten them for not helping, well, that unites that party.”
Yet Democrats give Mr. Schumer — song-belting, frequently badgering, endlessly frenzied — credit for his tireless attention to senators from every faction, and for quiet outreach to Republicans who he thinks could be partners down the line.
He has worked carefully — far more than Mr. Reid, many Democrats agreed — to be almost relentlessly inclusive, talking with them at all hours of the day, over every manner of Chinese noodle, on even tiny subjects, to make them feel included in strategy. Recently, as he sat in a dentist’s chair waiting for a root canal, he dialed up Senator Richard Blumenthal of Connecticut to talk about a coming judiciary hearing concerning Donald Trump Jr.
“I think he makes it look easier than it is,” Mr. Blumenthal said about Mr. Schumer.
Mr. Trump’s election stunned him.
Mr. Schumer’s original plan after the election was to find a way to work with his fellow New Yorker on issues where he thought they might align, such as an infrastructure bill.
“I take what’s given me,” Mr. Schumer, 66, said in a (shoeless) interview in his Capitol Hill office right off the Senate floor, one festooned with portraits of his idols (Eleanor and Franklin Roosevelt, Lyndon B. Johnson), maps of New York and mildly goofy photos with other Democrats.
Fleeting dreams of using Mr. Trump’s populism to triangulate against a Republican-controlled Congress dissolved, he said, when Mr. Trump instead decided to move right away to repealing the Affordable Care Act. So Mr. Schumer turned to an opposition agenda, doing everything within his limited powers to slow, block or obviate Mr. Trump’s agenda.
“We’re in the minority, so we’re not making policy,” Mr. Schumer said. “We have to know when to dance and when to fight. The Trump administration has made it harder to dance.”
For the fight, Mr. Schumer held together his disparate group of red state moderates, left-wing resistance fighters, hard-core policy wonks and everything in between, forming a partisan blast wall against Republican efforts to repeal the health care law, in part via maddening delays of basic Senate business.
Mr. Schumer’s schmoozing abilities have been important. “He knows who I am,” said Senator Joe Manchin III, Democrat of West Virginia, who is among the party’s moderates in a state Mr. Trump won handily and who has largely opposed Mr. Trump’s agenda.
“I tell him when I think he is moving too far to the left,” Mr. Manchin said, as when Mr. Schumer pushed to filibuster to block Mr. Trump’s nomination of Judge Neil Gorsuch to the Supreme Court. “There were no conversations with Harry.”
It was not an article of faith that Mr. Schumer could do what he has done. With several Democrats up for re-election next year in states Mr. Trump won, both Republicans and Democrats assumed that those vulnerable lawmakers would be tempted to try to help unravel the health care law, vote for large tax cuts and the like.
“He makes it clear to people that the opposition is about Medicaid cuts for the middle class and working class, not just the poor,” Mr. Blumenthal said, explaining the rationale for fighting the health care law repeal. “It’s about opioid treatments, not just reproductive rights.”
Mr. Schumer’s central weapon is procedural tricks to slow Mr. Trump’s nominees, something that infuriates Mr. McConnell. “I don’t like it, and we are not going to do it as a practice,” Mr. Schumer said, but “when you’re choosing a cabinet nominee, especially a controversial one, it makes sense.’’
All told, he said, his relationship with Mr. McConnell is an improvement over Mr. McConnell’s with Mr. Reid. Mr. Schumer has repeatedly told Mr. McConnell that Democrats would ease up on their obstruction once health care was behind them.
“I’ve known Chuck a long time, and he represents his state and his caucus well,” Mr. McConnell said in an email before the health care vote. “And while New York and Kentucky are very different places, we respect and work well with each other — even if we are trying to achieve very different goals. The Senate as an institution functions through cooperation and constant conversations with the other side of the aisle.”
Mr. Schumer committed one slight toward Mr. McConnell that baffled even his closest allies, voting against letting Mr. McConnell’s wife, Elaine Chao, become secretary of transportation.
“She would not commit to spending money on transportation,” Mr. Schumer said, even though most other Democrats gave her the nod. The move frosted Mr. McConnell, several Republicans said.
Mr. Schumer has watched Republicans struggle with moving from, in Speaker Paul Ryan’s words, an “opposition party to a proposition party” — a major reason that Mr. Schumer and other Democrats recently rolled out a new economic message and policy platform for Senate and House Democrats.
“He has recognized Democrats need a positive agenda,” said Jim Manley, a former aide to Mr. Reid. “And has begun putting that face before his caucus and the public.”
Mr. Schumer seems to approach this with his usual blithesome manner, singing show tunes and the Shirelles as he races from phone call to meeting, sliding away from potential pests, a cellphone pressed to his face.
“I love every single member of my caucus,” he said. Oddly, this is likely true.