Let’s imagine for a moment that Donald Trump isn’t going to be the Republican nominee for president. There are three ways this fantasy — and it is likely nothing more than a fantasy — becomes a reality.

One is that something Trump does is just so outrageous and disgusting, it knocks him out of the race and by default Ted Cruz becomes the nominee. (You can stop laughing ruefully now; I’m sure we all know now that’s not going to happen.)

The second is that Ted Cruz wins 80 percent of the Republican delegates going forward, passes Trump and takes it on the first ballot at the convention in July. At the moment, no one seems to believe this scenario is viable — not even the Cruz camp, which doesn’t bother talking it up.

The third is that Trump doesn’t secure enough delegates to win it on the first ballot and the GOP rises up on subsequent ballots to take it away from him and give the nomination to someone else.

This is possible. Indeed, it’s exactly what Cruz and John Kasich — the candidate with no shot who is staying in even though he won as many delegates on Tuesday night as I did — are counting on to propel them to the nomination.

They shouldn’t be. At all. In fact, they might as well write their own concession speeches right now.

Let’s play the anti-Trump scenario out. It’s July; the convention is coming in a few weeks. After the final primaries in California and New Jersey on June 7, Trump ends up with 1,000 to 1,150 delegates, short of the 1,237 he needs to secure a majority of the delegates.

Meanwhile, polling shows he’d get crushed by Hillary Clinton.

Moreover, state-by-state polling suggests that not only isn’t Trump taking states from Hillary but that she’s on track to take states away from the GOP’s 2012 take — North Carolina, for example, and potentially Arizona (with its 37 percent Hispanic voter registration). A poll earlier this week suggested Clinton might even take rock-ribbed Republican Utah if Trump is the nominee. (And as goes Utah, so goes Idaho.)

A comfortable Obama electoral lead in 2012 bids fair to become a Hillary electoral landslide. That would almost certainly mean the Senate would flip from Republican to Democratic control, with a strong possibility the House might flip to the Democrats as well.

Under these conditions, even the threat of chaos and violence from Trumpkins who seem not to understand the meaning of the phrase “a majority of the delegates” would be worth testing if somehow the GOP could settle on a candidate who might not win but who might change the catastrophic dynamic of the race.

This is the scenario Cruz and Kasich are hoping for. And in hoping for it, they are talking themselves into political oblivion.

Look, fellas: If Trump doesn’t get enough delegates to win, why would a GOP let entirely loose from primary and caucus results and able to choose anyone as its nominee turn to two candidates who received even fewer delegates than Trump did?

Would this panicked GOP look at Potential Nominee Cruz and foresee a shift in its fortunes? Why would it? Cruz has yet to demonstrate he has a national constituency. Alas for him, the movement he wanted to lead — conservative white people who, according to a delusional theory unsupported by evidence, didn’t turn up to vote for Mitt Romney in 2012 by the millions and cost the GOP the election — has a candidate: His name is Trump.

Does Kasich have a following? Yes, he does, of people who still cry when they listen to “Eleanor Rigby” and its invocation of “all the lonely people” and who want a hug because their Aunt Minnie has the shingles.

Why would the GOP think its chances of prevailing in November would be notably enhanced by turning to either of these guys rather than to, say, Paul Ryan (who at least was the vice presidential nominee on a ticket that got 61 million votes) or even Mitt Romney (who was at the top of the ticket that got 61 million votes)?

The logic is clear. Cruz’s political rise in Washington came when he won by losing. That is to say, he got himself famous by opposing his own party, forcing a government shutdown, not getting what he wanted and claiming he and his followers had been screwed by Establishment Republicans. It worked for him.

It’s not going to work for him now. You can’t win the GOP nomination by losing.

Ted Cruz should stop playing for second, because if he comes in second, he’s not going to be the nominee. The only way he gets to grasp the brass ring is to beat Trump outright.

It’s a nearly insuperable challenge. But there it is.

Here’s exactly how a contested convention would actually work: