Senate Democrats on Tuesday lost the battle to stop President Trump’s pick for secretary of education. But on bigger battles ahead, the Democrats have a powerful weapon — and they intend to use it.

Republicans control both houses of Congress and the White House. Yet Senate Minority Leader Chuck Schumer boasts that he can block Trump’s legislative agenda.

“He won’t be able to do it,” Schumer says confidently.

What allows Schumer to thwart the majority’s will and paralyze the Senate? Not the Constitution.

The answer is a centuries-old Senate practice called the filibuster. Senators in the minority could take the floor and talk endlessly, never agreeing to formally end debate so the majority could vote. They’d talk the legislation to death, in the process shutting down all other Senate business. The House never permitted it, always allowing a simple majority to shut down debate.

In the Senate, the idea was to make sure the minority was heard. But over the years, the rule was exploited to actually stop legislation altogether.

Southern Democrats used it to block anti-lynching legislation in the 1930s and civil-rights laws in the 1950s. Not until June 10, 1964, were anti-segregationists able to muster enough votes under Senate rules to cut off a filibuster on a major civil-rights bill — after a staggering 60 days of debate.

Then in 1975, the Senate modified the filibuster. Senators could now close debate and bring legislation to the floor if they had 60 votes to do it. Since then, the minority doesn’t have to monopolize the floor and debate endlessly, shutting down all business. Threatening to do so is enough to hold up a bill.

Call it a fake filibuster. Right now, Republicans have 52 Senate seats, not enough to stop Democrats from filibustering legislation and Supreme Court nominees.

In recent years, Republicans have benefited from the 60-vote rule. During President Barack Obama’s first two years in office, the Republican Senate minority used it to kill pro-union legislation, the Dream Act, gun control and a federal minimum-wage hike.

Now Democrats want payback. Minutes after Trump announced his Supreme Court nominee, Schumer proclaimed that “on a subject as important as a Supreme Court nomination,” there have to be 60 votes to move forward.

That’s politics. But DC insiders talk about the 60-vote rule as if it were sacrosanct, the holy grail of democracy. “It’s the way our founding fathers set it up,” says Sen. Bill Cassidy (R-La.).

Sorry. That’s not the case.

The framers designated five circumstances requiring a supermajority: convicting an impeached president or other high officer, amending the Constitution, ratifying a treaty, overturning a presidential veto or expelling a member of Congress. That’s the whole list, and passing laws and confirming nominees aren’t on it.

At the Constitutional Convention, the framers considered requiring a supermajority in the Senate to pass laws, but repeatedly rejected the idea.

James Madison explained in Federalist No. 58 that it would give the minority control over the majority. The “principle of free government would be reversed.” Requiring laws to pass two houses of Congress and giving the president a veto were better ways to promote wise lawmaking.

Alexander Hamilton warned that a supermajority requirement would cause “tedious delays,” as it had under the failed Articles of Confederation. Just what we’re facing now.

Meanwhile, McConnell, a Senate lifer first elected in 1984, defends the 60-vote rule, telling colleagues not to “act as if we’re going to be in the majority forever.”

NYU law professor Burt Neuborne deplores these “rules that scratch my back today and yours tomorrow.” They protect career politicians more than the public: The 60-vote threshold dashes voters’ hopes that an election can produce real change.

Some call dropping the filibuster “going nuclear.” Actually, it would be a return to what the framers envisioned — “going original.”

Betsy McCaughey is a senior fellow at the London Center for Policy Research.