Donald Trump began the day on Monday with a candid expression of his isolationist foreign policy. He told The Post’s editorial board that even our commitment to NATO was up for debate. (“When you look at the kind of money that our country is losing, we can’t afford to do this. Certainly we can’t afford to do it anymore. … NATO is costing us a fortune, and yes, we’re protecting Europe with NATO, but we’re spending a lot of money.”) To a greater degree than President Obama and certainly Hillary Clinton, Trump looks upon allies as a burden (“South Korea is very rich. Great industrial country. And yet we’re not reimbursed fairly for what we do.”) and sees neither an obligation to exert U.S. leadership nor any benefit derived therefrom. Hard as it is for Republicans to imagine, Trump would be worse for our allies, worse for the cause of freedom, worse for stability in the Middle East and therefore worse for U.S. national security than Obama.

It is a world view entirely at odds with that of the pro-Israel community, which understands that a strong United States and strong Israel are essential components of our national security. At the American Israel Public Affairs Committee gathering, Trump was forced for the first time in the campaign to operate with a teleprompter. While his verbal tics (“believe me”) and cringe-worthy boasts (“I’ve studied this [Iran] issue in greater detail than almost anybody”) littered the speech including some real whoppers. On marching in a pro-Israel parade in 2004 he proclaimed, “It was a very dangerous time for Israel and frankly for anyone supporting Israel — many people turned down this honor — I did not, I took the risk.” That is up there with confusing boarding school with military service.

The rest of the written speech contained plenty of red meat and standard-fare applause lines — slamming the United Nations, denouncing a peace plan imposed from afar and declaring, “When I become president, the days of treating Israel like a second-class citizen will end on Day One. I will meet with Prime Minister Netanyahu immediately.”

And yet even with a written text, his delivery was awkward and applause lines often fell flat. The teleprompter did not change the obvious: His position on major issues is fuzzy if not incoherent. He is going to enforce the Iran deal. And he is going to dismantle it. He is worried about Iranian aggression, yet he has repeatedly said he would leave Russia and Bashar al-Assad, Iran’s best allies, to their own devices in blood-soaked Syria. He repeatedly has said he was uncertain about moving the embassy to Jerusalem; he nevertheless got applause for reading off the teleprompter: “We will move the American embassy to the eternal capital of the Jewish people, Jerusalem — and we will send a clear signal that there is no daylight between America and our most reliable ally, the state of Israel.”

The problem, of course, is that one needs more than a teleprompter to get through a campaign and to serve as president. Trump again and again demonstrates that without getting lines fed to him by a teleprompter he lacks a coherent world view, an understanding as to how the United States needs to project its influence (or even whether it should do so) and respect for American democratic traditions. As he careens through the primaries, ripping the GOP asunder, tearing at the fiber of American democracy and living up to his image as an arrogant bully, Republicans should understand how many voters will flee to the outstretched arms of Clinton, warts and all. If Trump is the best the GOP can come up with, it deserves to be beaten — badly.