President Trump, time to read up on Harry Truman. The president has mentioned Andrew Jackson as a role model, yet as Congress careers toward a recess it hasn’t earned, “Give ’em Hell Harry” might be the better history teacher. Truman, remember, got his back up and cut short Congress’ vacation at a crucial moment in 1948.

What a move that would be for Mr. Trump. Congress has failed to pass a tax bill or repeal ObamaCare — or deal with the debt ceiling. Yet the lollygagging lawmakers are scheduled to take off the whole month of August for a taxpayer-funded vacation.

Clearly some members of Congress see how absurd that looks. Particularly in a season when Americans are prepared to sink more than $50 million into a single congressional race, as they just did in Georgia’s 6th district.

They’re desperate for action.

No wonder the House Freedom Caucus has been agitating for Congress to forgo its recess and work straight through Labor Day. One senator, David Perdue, a Republican of Georgia, reckons, according to the Hill, “there’s a majority that probably supports being here.”

Yet with the GOP “still sharply divided on healthcare and tax reform,” the Hill reports, “it looks increasingly possible that Republican lawmakers will leave town in July for a month long break without any major accomplishments.”

The opportunity for Mr. Trump lies in his constitutional power to convene both houses of Congress almost whenever he wants. He could declare that if Congress tries to skedaddle, he’ll call it right back.

Truman was the last modern president to have pulled off this stunt. On July 26, 1948, fewer than four months before he was up for re-election, he used his nomination acceptance speech to block the congressional recess.

Truman wanted Congress to deal with civil rights, social security and — yup — health-care legislation. He reckoned that the crisis qualified as one of the “extraordinary occasions” on which the Constitution lets him convene a special session.

Plus, Truman’s job-approval rating was, at 36 percent, even lower than Mr. Trump’s current standing, which Gallup has at 38 percent. No doubt Truman looked at his job-approval numbers and concluded he had little to lose by taking a gamble.

There’s a big difference between then and now. Truman, a Democrat, was ordering back to Washington a Congress controlled by the Republicans. And they were madder than the New York Times is at our victory in the Cold War.

The Constitution required Congress to answer Truman’s beck. But Senator Robert Taft, an Ohio Republican, blocked any legislation. Truman had the last laugh by running against the Republican “do-nothing Congress.”

Now, of course, it’s the Democrats who are trying to prevent action on the Hill. Things are so bad that, according to a headline in the Times, the Democrats will deal with the health bill by trying to “run out the clock.”

It adds up to a perfect situation for President Trump to exert his powers. Particularly since the un-passed legislation deals directly with promises he made during the 2016 campaign.

Economist Larry Kudlow, one of the first to call for abandoning the recess, wants Congress to focus on tax cuts. He went to the White House earlier this month to try to make his case.

The key is lowering the corporate rate to 15 percent from 35 percent. Mr. Kudlow would also have Congress permit expensing new business investment. And establish “a small, one-time, 10 percent percent rate for the repatriation of offshore cash.”

Mr. Kudlow would put his tax plan into the same reconciliation bill that could be used for health-care reform. The idea is to redeem the president’s pledge to focus on creating the conditions for a jobs boom here in America.

A move by Mr. Trump to force Congress back to Washington during August recess would do one more thing. It would demonstrate the president’s capacity to lead, particularly when his own staff seems asleep at the switch.

Only yesterday Mr. Trump’s spokesman, Sean Spicer, was asked about the recess and whether the president is satisfied with the “pace” at which Congress is moving. It’s “a little out of our hands,” he muttered.

What kind of talk is that from the camarilla of a president who holds the power to call Congress into a special session? It doesn’t sound like the Donald Trump Americans voted for. Or the Truman who went on to win a second term.

This column first appeared in the New York Post.