The Ted Cruz-John Kasich plan to tag-team Donald Trump is a desperation move — showing that both camps know Trump is solidly on track to the GOP nomination.

The plan has Kasich skipping out on campaigning in Indiana while Cruz does the same in Oregon and New Mexico. It’s all to stop Trump from winning on the first ballot at the convention.

Two big problems. First, they need voters to switch from their preferred candidate to a guy they dislike, just to stop Trump — and most Americans just don’t vote that way.

Second, the scheme ignores the fact that neither Cruz nor Kasich actually has a viable strategy for winning the White House.

Trump does: Get the nomination, rally the party behind him and use his proven appeal with independents and Democrats to beat Hillary Clinton.

Maybe he won’t be able to pull it off, but at least it makes sense.

From the start, Cruz has assumed he can win in November running purely as a true-blue conservative. He claims that’s the 1980 Ronald Reagan approach — but it’s not. It’s what Barry Goldwater did en route to his landslide loss in 1964.

Nor has Cruz even been able to win over most Republicans. His hope to grab the nomination rests on insider games that will be useless in the general election.

Kasich figures he’s inoffensive enough to win over moderates against Clinton — but he has absolutely no path to the nomination. Marco Rubio still has more delegates, and a convention full of Trump and Cruz supporters will never settle for the Ohio governor.

Trump will have a yuuge night Tuesday, and is a sure bet to carry several more states later on, including winner-take-all New Jersey. His last two opponents are reduced to Hail Mary tactics before the real battle — against Clinton — even starts.

The fat lady of the GOP opera hasn’t sung yet. But she’s warming up.