If the Senate’s governing principle can be reduced to this, “Saying no is easier than saying yes,” then it makes sense that leading the caucus so often focused on stopping stuff is much less demanding than being in charge of the group that’s always held responsible for getting things done.

Six men have personified this lesson during the past 40 years, former senators who had both responsibilities while they were floor leaders. For Democrats Robert C. Byrd, Tom Daschle and Harry Reid, as well as for Republicans Howard H. Baker Jr., Trent Lott and Bob Dole, solid arguments can be made that their stewardships were much more successful as minority leaders than as majority leaders.

The same is on course to come true for Mitch McConnell — although, to be fair, he’s not done being majority leader yet, so his record in that job has a theoretical shot at equaling or exceeding the solid performance he turned in during eight years shepherding a Republican minority.

All of which leads to the breakout senatorial star of the season.

Charles E. Schumer, who spent his first eight months as Democratic leader operating successfully from the “just say no” manual, has transformed this fall’s congressional dynamic with an altogether different maneuver.

He got to “yes” with President Donald Trump on a matter of much more strategic than substantive import, which now positions him to have as much leverage as any minority leader — over a rash of issues coming to pivot points more or less simultaneously at year’s end.

Schumer accomplished this by persuading the president, with the help of House Minority Leader Nancy Pelosi, to support an extension of Treasury’s borrowing powers and uninterrupted government funding, but only until the second Friday after Thanksgiving.

The pact blindsided McConnell and Speaker Paul D. Ryan, who were at the same Oval Office meeting last week to press for an increase in the debt limit lasting much longer. But within two days, the measure had sailed through Congress on lopsided bipartisan majorities.   

With that deal, Schumer “just made himself the most powerful man in America for the month of December,” Republican Sen. Ben Sasse of Nebraska lamented in a speech to his colleagues, because he’ll be “the key man in all negotiations” climaxing before lawmakers are sent home for the holidays.

A comprehensive spending package, good for 10 months, will need to win passage by Dec. 8 to get past the next threat of a partial shutdown. Another vote by then to lift the cap on the national debt will be necessary to ward off talk of government default.

Insurance companies are clamoring for legislation to stabilize the individual health policy market now that the 2010 health care law has survived the GOP repeal-and-replace crusade. Hundreds of thousands of young people who entered the country with their undocumented parents don’t want Congress to wait until Trump’s new March deadline before shielding them from deportation and granting them permission to work.  

Support across the aisle?

Primarily because each exposes deep fissures in the GOP ranks, all those measures will require significant support across the aisle to get through Congress — whether as a series of standalone bills or in one or more combination packages.

Some Democratic votes will be counted on in the House, but there will be an even more acute need for Democratic senators to stand down from their default eagerness to filibuster whatever legislation comes along. And that is what gives Schumer his first big opening, since taking his big job in January, to be a minority leader who’s central to accomplishment instead of an avatar of obstruction.

Much has been made about the potential for a lasting relationship between the two aging baby boomers from New York City’s outer boroughs — Queens native Trump is four years older than Brooklyn-born Schumer, who turns 67 in November. Both share similar competitive drives, personal aggressiveness, cravings for media attention, pride in their negotiating abilities, and confidence in their powers to persuade middle-class voters.

But while they have crossed paths for decades in the world of Manhattan charity galas and big-money fundraising, with Trump and his immediate family donating almost $20,000 to Schumer’s campaigns over the years, their grip-and-grin acquaintance has never matured into any sort of schmoozing friendship or even a golf date.

Future alliances between them, in other words, are likely to be transactional affairs — bonds formed only when both of them conclude they’d rather come up with a deal than remain in the good graces of their bases.

Their past histories point to a future when Trump, a latecomer to the GOP and arguably the least ideologically grounded president in modern times, will be eager to go there much more often than Schumer, who is under pressure to help hold at bay the simmering civil unrest pitting Democratic pragmatists against progressives and those whose abiding goal is to block the president at every turn.

Ever since the election, Schumer has said he would not be out to obstruct Trump as an end in itself. And, at the start of the year, anyway, it seemed likely the minority leader would prove amenable to going the extra mile with the new president — mainly in hopes of making life easier for the 10 of his fellow Democrats getting ready to seek re-election next year in states that Trump carried.

That dynamic changed, however, once Trump decided to make repealing and replacing the health care law his first big legislative push (without any input from across the aisle) and Democrats provided unanimous opposition to dismantling the law right through the GOP effort’s denouement in August.

Which path?

Now, the three-month kicking of the fiscal can that Schumer and Pelosi sold to Trump has put the senator, especially, at an early crossroads in his leadership career. He has until about Thanksgiving to decide which path to take.

That Trump, whether impulsively or not, so readily embraced last week’s Democratic leadership offer may prompt Schumer to conclude he has the leverage to secure much more of the same by the end of the year — in time for Senate Democrats to start running in 2018 as essential players in creating a “do-something” Congress.

Such a wish list would include modest domestic spending increases, abandonment of Trump’s most dramatic budget cuts, a legislative bolstering of the individual insurance market, and turning the Obama-era deportation relief for undocumented childhood immigrants into law.

But the trade-offs that might be demanded in return, coming not only from the White House but also from GOP leaders who have hardly lost their relevance, could instead prompt Schumer to decide that minority Senate Democrats are better off backing away from the bargaining and running the traditional party-of-presidential-resistance campaign next year.

Accepting some cuts to environmental protection, substantial deregulation of Wall Street, a disproportionate spending boost for the Pentagon and even a symbolic down payment on Trump’s border wall could all prove too much for even the most politically imperiled centrist Democratic senators to bear.

Overlaying Schumer’s big choice, meanwhile, is something he seems powerless to control — Trump’s own appreciation for having “Chuck” in his corner.

The president has shown an ability to move from make up to break up at lightning speed, especially when he feels the smallest measure of disloyalty. And so Washington has become littered over the past seven months with people who went from being the new president’s newest best buddies to being personae non gratae in the West Wing.

Schumer, labeled “head clown” and “Cryin’ Chuck” in presidential tweets just months ago, can surely expect more of such derision as soon as Trump perceives he’s being a smidgen less than entirely cooperative.

No other Senate minority leader has taken such public abuse from a president, and Schumer’s baseline decision may come down to having to say “no” or “yes” to accepting such ridicule in the pursuit of a larger strategic goal.