After dispatching Sen. Ted Cruz in the Arizona primary Tuesday, Donald Trump’s real opposition is not another candidate but a numeral — 1,237.

That, of course, is the magic number Trump needs to cinch the GOP nomination for president before the Republican National Convention in July.

Immigration has been the centerpiece of Trump’s improbable run to the top of the GOP field, and in no state does that issue resonate more than in Arizona, where the New York billionaire had the support of a pair of well-known foes of illegal immigration — former Gov. Jan Brewer and Maricopa County Sheriff Joe Arpaio.

“Much bigger win than anticipated in Arizona,” Trump tweeted. “Thank you, I will never forget!”

Cruz crossed the 50 percent threshold in the Utah caucuses and collected all 40 of that state’s delegates, but Trump finished the night with a wider overall lead than he had when the day began. The margin now stands at about 285. It remains a possibility that Cruz and Gov. John Kasich could still hold Trump under 1,237 delegates, however. Assuming Trump holds onto his victory in the March 15 Missouri primary — the results are not yet official  — he will have 750 delegates after Tuesday’s voting.

That is 487 shy of the goal. To get there, Trump would have to win about 53 percent of the 922 delegates still to be allocated. But a chunk of those delegates are outside the control of regular Republican voters. Nine delegates from American Samoa and 28 from North Dakota will go to the convention unbound. In addition, 54 of Pennsylvania’s 71 delegates are elected directly in the primary and can vote for any candidate they wish.

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Finally, Colorado has a complex system for picking delegates involving district and state conventions in April. Some of those delegates are pledged to specific candidates, while others are running as free agents.

Getting to 1,237 only with delegates who will be committed through primary and caucus voting would require Trump to win about 60 percent of those remaining. That is a more difficult challenge. If he falls short, he still could win the nomination on the first ballot by wining the support of enough unbound delegates.

Just after midnight, Trump cast an eye toward the difficult task of unifying the party.

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“Hopefully the Republican Party can come together and have a big WIN in November, paving the way for many great Supreme Court Justices!” he tweeted.