In a “Dear Colleague” letter on Jan. 3, Senate Majority Leader Chuck Schumer issued a warning: If Republicans continued to block the Senate from passing two sweeping elections-related bills supported by Democrats, he wrote, then the chamber would “debate and consider changes to Senate rules on or before January 17.” That was a threat, as everyone understood, to invoke the “nuclear option” and blow up the filibuster. If successful, Democrats would no longer require 60 votes to pass their controversial measures; a bare majority would suffice.

That was on Monday. On Tuesday, Democratic Senator Joe Manchin of West Virginia came out against the nuclear option, saying he would find it “very, very difficult” to support any unilateral move to kill the filibuster. So did Senator Kyrsten Sinema of Arizona. During a Democratic caucus lunch, the news site Axios reported, she told her colleagues that “she will not support any effort to get rid of the 60-vote threshold.”

So much for Schumer’s threat to go nuclear. The filibuster is safe for now.

Is that a good thing or a bad thing? Arguments can be made both ways, but my view has long been that the filibuster ought to be reformed by returning to the rules that prevailed before 1970. The Senate should revive the old “talking filibuster,” under which a senator or group of senators could indefinitely forestall a vote on any measure by the means Jimmy Stewart dramatized in “Mr. Smith Goes to Washington” — taking to the floor to speak and refusing to sit down until the majority agrees to compromise. When a filibuster was in progress, all other Senate business came to a halt.

Those two crucial stipulations — a filibuster had to be conducted in person and it superseded other Senate activity — made the maneuver both powerful and rare. Consequently, it was a weapon deployed with great caution. During the entire 19th century, for example, there were fewer than two dozen filibusters.

But in 1970, the rules changed. Under a new two-track system, a bill being filibustered would be put aside while the Senate took up other matters. Senators no longer had to emulate Jimmy Stewart to block a piece of legislation — they merely had to threaten to do so. In effect, the filibuster became a blackball, which could be overcome only with supermajority support. Before long, it was taken for granted that every significant bill needed 60 votes to pass.

Though the filibuster continued to exist, its core purpose had been inverted: A parliamentary tactic meant to ensure debate and encourage compromise had become an artificial gimmick to prevent debate. Mixed with the toxic partisanship and angry polarization that now dominate American politics, the modern filibuster’s impact has been to make the Senate more dysfunctional and less deliberative.

And then there’s the hypocrisy.

Dozens of Democrats are decrying the filibuster as an antidemocratic travesty, a threat to voting rights, an unconscionable obstruction of the will of the majority — even, as former president Barack Obama called it, a “Jim Crow relic.” Yet as recently as 2017, a majority of Senate Democrats signed a bipartisan letter defending the filibuster and “opposing any effort to curtail the existing rights and prerogatives of Senators to engage in full, robust, and extended debate.”

What changed? Democrats and their allies claim that the stakes now are so high, and the measures they support so urgent, that the nation can no longer afford any impediment to legislating by straight majority rule.

Here’s a simpler explanation: In 2017, Senate Democrats were in the minority and a Republican was in the White House. Back then, Democrats were making vigorous use of the filibuster to block Republican priorities — over the next four years, they would filibuster hundreds of bills and nominations — while Donald Trump was the one clamoring to eliminate the 60-vote rule. “Republican Senate must get rid of 60 vote NOW!” Trump tweeted angrily. “It is killing the R Party, allows 8 Dems to control country. 200 Bills sit in Senate. A JOKE!”

In a thoughtful Politico essay a few months ago, Ronald Weich, dean of the University of Baltimore Law School and a former top aide to senators Edward Kennedy and Harry Reid, warned his fellow liberal Democrats that if they kill the filibuster today, they will find themselves in a “nightmare” tomorrow.

“Progressives pushing to end the filibuster are suffering from a bad case of amnesia,” Weich wrote. “The past three decades, in fact, are filled with moments when the filibuster prevented Republicans from pushing through legislation that would have made America a far darker place.” Personally, I think that some of the GOP legislation Democrats blocked would have made life in America considerably brighter. But Weich’s essential point is that if Democrats deep-six the filibuster, they will enjoy no more than a short-term victory. Sooner or later, perhaps as early as next January, Republicans will regain control of the Senate. At which point — if the filibuster has been nuked — there will be nothing to prevent them from repealing with 51 votes whatever the current Senate passes by a similar bare majority.

In 2005, when Republicans were in the majority, they were tempted to do to the filibuster what Schumer and most Democrats want to do now. Obama, then a senator from Illinois, understood what was on the line.

“I understand that Republicans are getting a lot of pressure to do this from factions outside the chamber,” he said in a floor speech. “But we need to rise above an ‘ends justify the means’ mentality because we’re here to answer to the people — all of the people — not just the ones wearing our party label…. One day Democrats will be in the majority again, and this rule change will be no fairer to a Republican minority than it is to a Democratic minority.”

It’s one of the oldest rules in two-party politics: What goes around comes around. If only both parties could manage to remember it — at the same time.

(Jeff Jacoby is a columnist for The Boston Globe).