Back in December, when Donald Trump’s prospects in the primaries still seemed uncertain, I asked several leading political pollsters about whether they thought he could win a general election. And one of them, a Democratic pollster named Fernand Amandi, made this striking remark.

"His only shot to win in the general is the 'I told you so' campaign, if there is a major, major terrorist attack," Amandi told me. "In the casino magnate style that has always been his life and persona, he is betting it all on this one issue."

Now, after the Pulse nightclub shooting in Orlando, it seems clear that Trump is indeed gambling that fears of terrorism will sweep him into the White House.

It’s also clear that he has a scarily simple plan to take advantage of those fears — and what’s even scarier is that because it's never really been tried in recent decades, we really don't know whether it will work.

Trump is making a clear, digestible argument

In a speech responding to the shooting Monday, Trump made the following case that was bigoted, factually challenged, and previously beyond the pale for American politics at the presidential level — but also clear, easily digestible, and potentially emotionally appealing to many Americans.

1) You are not safe. "Radical Islam is coming to our shores," Trump said.

2) There is a simple, commonsense way you could be kept safe. "The only reason that the killer was in America in the first place is because we allowed his family to come here. That is a fact, and it’s a fact we need to talk about."

3) It’s by keeping the people who commit terrorist attacks — Muslims — out of our country. "When I'm elected, I will suspend immigration from areas of the world where there is a proven history of terrorism against the United States, Europe, or our allies, until we fully understand how to end these threats."

4) The politically correct media and Democrats won’t be honest about this and therefore won’t take this obvious measure to keep you safe. I will. "They have put political correctness above your safety and before all else. I refuse to be politically correct. I want to do the right thing. I want to straighten things out. And I want to make America great again."

This hasn’t been tried in recent decades at the presidential level

Trump’s argument, of course, leaves unmentioned that terrorist attacks are committed by a minuscule minority of Muslims, that an incredibly large majority of Muslim immigrants to the US are completely peaceful, that Americans of all races commit mass shootings, and that the past two presidential administrations have believed that framing this conflict as one of Americans against Muslims is counterproductive. And his speech was misleading and wrong in all sorts of other ways.

Yet it’s not really aimed at making a rational point — it’s aimed at appealing to the fears that exist at the back of many Americans’ minds.

Trump is peddling a simplistic solution that any voter can understand: To stop terrorism, keep out Muslims. It’s a whole heck of a lot simpler than the complex, multifaceted plan Hillary Clinton laid out earlier Monday.

We really don’t know how popular such a message will be because it hasn’t yet been tried at the highest levels of American politics.

Days after the 9/11 attacks, President George W. Bush took a stand against anti-Muslim bigotry in a speech at a mosque, saying that "Islam is peace." And throughout most of his administration, though his military interventions became intensely controversial, he resisted pressure from the right to define the conflict as one of America against Islam.

But many Americans are not particularly well-disposed toward Muslims and Islam. A Brookings poll conducted last year showed that only a narrow majority of Americans — 53 percent — said they had favorable views of "Muslims." And a sizable majority — 61 percent — said they had unfavorable views of "Islam." (Note that this poll was conducted before the attacks in Paris, San Bernardino, and Orlando.)

Despite all this, and despite many politicians fomenting fears of Islamophobia, no one significant did anything as extreme as proposing a ban of Muslim immigration — until Trump did last fall.

Once Trump did cross that line, he was bitterly condemned by many GOP elites — even Dick Cheney said the idea "goes against everything we stand for and believe in." But as Byron York has written, exit polls show that large majorities of Republican primary voters thought Trump’s idea was just fantastic.

We’ve been fortunate enough that we’ve never gotten a chance to learn whether an argument like this — blatantly proposing to block an entire class of people from the country — could catch on with a general election electorate. And I fervently hope it doesn’t.

Unfortunately, though, we're going to find out whether it can.