By David Gergen
CNN Senior Political Analyst

Editor’s note: David Gergen is a senior political analyst for CNN and has been a White House adviser to four presidents. A graduate of Harvard Law School, he is a professor of public service and co-director of the Center for Public Leadership at the Harvard Kennedy School. Follow him on Twitter: @david_gergen. The opinions expressed in this commentary are his.

Two weeks ago, after his decisive win in Wisconsin, it appeared that the odds for winning the GOP presidential nomination had suddenly and unexpectedly shifted in favor of Sen. Ted Cruz.

Donald Trump was then on the ropes, as he had failed to assure voters about fights breaking out at his rallies, engaged in needless attacks on Heidi Cruz, and then — outrageously — said that women who obtained illegal abortions should be criminally punished. Rarely have we seen so much self-destruction by a front-runner, so much so that one wondered whether Trump had a death wish.

Coming off his primary victory over Trump in Wisconsin, Cruz had an opening to put away The Donald, perhaps forever. And since then, Cruz has played the inside game extraordinarily well, winning a string of caucuses and peeling away a number of avowed Trump delegates who swore they would support Cruz on a second ballot.

But as we have seen in this most peculiar of all peculiar campaigns, two weeks can change the world. And so they have, climaxing in Trump’s thumping victory in New York on Tuesday night.

It’s too much to say that the odds now favor either Trump or Cruz — this Republican race could go in several different directions — but there is no doubt that Trump has come off the ropes, revived his campaign and poses a formidable threat to anyone who tries to stop him from the nomination.

What happened?

For one thing, Trump decided to shut up.

Instead of the steady stream of rants — each more jarring than the last — he lowered his profile and lowered his decibel level. Instead of viciously attacking people, he began attacking the political system, a lesser form of demagoguery.

He isn’t even calling in to the Sunday chat shows. He remains a narcissist, a misogynist, a sexist and more. But he also seems to know when people tire of having him in their face. (Can one even ask whether he is becoming “presidential”? Perish the thought!)

On the other side, Cruz didn’t seize the moment.

With Trump leaving the stage open, Cruz had to grab it for himself but somehow he hasn’t. He needed to drive home that Trump was unacceptable and that he was stepping into the breach. What came through instead was a muffled voice and scenes of a man clever enough to master the arts of inside politics but not inspirational enough to lead a great people.

Count Trump lucky that the New York primary was next; count Trump resilient that he bounced back so effectively, racking up a massive win. Cruz won his home state of Texas over Trump 44% to 27%; Trump won his home state of New York over Cruz by around 60% to 15%. (Cruz even wound up in third in New York.)

Of course, victory does not yet give Trump an easy path to secure 1,237 delegates before the GOP convention. But in politics, emotions often count as much as math. Psychologically, the tide could now reverse in Trump’s direction as he heads into next Tuesday’s five East Coast primaries with New York providing a fresh wave of momentum.

There are 15 primaries left in the campaign. Who knows?

Maybe Trump will make another horrendous mistake or Cruz will find a different voice, boosting Cruz once again. But looking over the pattern of primaries so far — where Cruz does well in the Midwest and Rockies while Trump has succeeded in the Atlantic seaboard and the South — it appears that Cruz could win at least five (starting with the key state of Indiana), but Trump could win as many as 10 (especially if he can sweep California, Oregon and Washington).

If Trump wins two thirds of the remaining primaries, guess what? He could still be short of the magical 1,237, but he will be a more commanding candidate heading to Cleveland.

He is already ahead of Cruz in total votes, so far by more than 2 million. He could easily go to Cleveland with that voter lead enhanced. Republican establishment types may often seem dumb, but they are not stupid: 62% of Republican voters (more than that in New York) are already saying that the nomination should go to the candidate with the most total votes, even if he doesn’t have a majority of delegates. If Trump comes to Cleveland more than 2 million votes ahead of Cruz and a fresh wind at his back, does it seem likely that the convention will deny him the crown in favor of Cruz?

Two weeks ago, to be sure, Cruz seemed to have the odds in his favor at a brokered convention. This small interval — and especially his New York loss — shifts the odds to dead even and perhaps better for Trump. Where is Teddy White when we need him?

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