Several of the 2020 Democratic presidential candidates are calling for an end to the filibuster, the Senate rule that makes it possible to keep any matter from coming to a vote unless a three-fifths majority — 60 senators — agrees to invoke “cloture” and cut off debate.

Elizabeth Warren is firmly in the anti-filibuster camp. “When Democrats next have power, we should be bold,” the Massachusetts senator declared this month. “That means … we should get rid of the filibuster.” Washington Governor Jay Inslee is also for scrapping the filibuster, which he calls “an antebellum rule in the Internet age.” Former Representative Beto O'Rourke of Texas and South Bend, Ind., mayor Pete Buttigieg say they are open to the idea.

But the filibuster has supporters, too. “I’m not crazy about getting rid of the filibuster,” Bernie Sanders said in February. He underscored his opposition last week, telling an interviewer: “Whether you’re in the majority or the minority, I think you have to protect minority rights.” Most of the other senators in the race share Sanders’s skepticism.

This is a curious debate. On most issues, the platforms of the 2020 hopefuls have been largely indistinguishable, so it’s refreshing when they find an issue on which they don’t march in lockstep. But the fate of the filibuster is something over which presidents have no authority. Whether it stays or goes, senators alone will decide. Why make it an issue in the presidential campaign?

The answer from some on the left is that as long as it takes 60 votes to get any controversial bill passed, Democrats’ boldest proposals will never be enacted, even if their party wins the White House and reclaims a majority in the Senate. So unless Democrats mobilize to overturn the filibuster, progressive goals like the Green New Deal or abolition of the Electoral College don’t stand a chance.

But that’s the reality on the other side of the aisle, too. Even with a Republican president and Senate majority, the GOP has not been able to repeal Obamacare or deliver the border wall President Trump craves. Trump himself is as adamantly anti-filibuster as Warren. “Republicans must get rid of the stupid Filibuster Rule — it is killing you!” he tweeted in 2018 in a typical denunciation.

It should give pause to moderate Republicans and Democrats alike that polarizing brawlers like Warren and Trump are the most prominent champions of killing the filibuster. If they got their way, nothing would be left of the speedbump that restrains a bare Senate majority from riding roughshod over minority opposition. That would turn the Senate into a smaller version of the House of Representatives, where the minority party has virtually no bargaining power and debate is sharply curtailed.

At their best, filibusters can be a valuable restraint on government overreach and reckless populism. Used with prudence and restraint, they protect the minority’s right to be heard, foster deliberation and compromise, and avoid precipitous decision-making.

The real problem with the filibuster isn’t that it exists, but that its use has become both routine and invisible. How this paradox came to be is a classic story of unintended consequences.

It used to be that any senator or group of senators could indefinitely block a vote on a bill the way Jimmy Stewart did in “Mr. Smith Goes to Washington” — by taking the floor to speak and refusing to stop until the majority agreed to give ground (or exhaustion overtook the speaker). Critically, while a filibuster was underway, all other Senate business was suspended

In 1970, then-Majority Leader Mike Mansfield introduced a “two-track” system, under which a bill being filibustered would be set aside so the Senate could take up other matters. The result was not what Mansfield doubtless expected — to make filibusters less desirable by stripping them of their power to gridlock the Senate. Instead, the number of filibusters soared. Or rather, the number of threatened filibusters soared. Those threats never had to be made good. The mere announcement that Senator X intended to filibuster Bill Y created a presumption that a supermajority would be required if the legislation was to move forward. Soon it was taken for granted that nearly every bill needed 60 votes to pass.

The solution to this problem isn’t to eliminate filibusters altogether, but to eliminate the two-track system that made them ubiquitous. Senators were far less likely to undertake a filibuster back when they knew that doing so would bring the Senate to a halt. It was a weapon used sparingly. During the entire 19th century there were only 23 filibusters. Since 1970 there have been more than 1,000.

The Senate can make filibusters rare again by making them real again. A determined minority should have the ability to resist passage of a measure they find intolerable. But they should also have to demonstrate their resistance the hard way — by taking the floor, staying on their feet, speaking without letup, and facing the consequences. Then and only then should it require a supermajority to cut off debate and vote.

The presidential candidates have been debating whether to get rid of the filibuster. What they should really be debating is how to get it back.

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