CLEVELAND – To chants of “2020, 2020,” Republican Sen. Ted Cruz on Wednesday left open the possibility of a second White House run even as Donald Trump arrived in Cleveland to accept the Republican presidential nomination.

“I don’t know what the future is going to hold. I don’t know what’s going to happen,” Cruz told his rowdy supporters, many of them cheering another bid. “But what I do know what remains unshakable is my faith in the men and women here.”

The freshman lawmaker with Texas-size political ambitions has stopped short of a full-throated endorsement of Trump, his bitter primary rival who often mocked him as “Lyin’ Ted.” Cruz was slated to deliver a prime-time convention speech, but no endorsement was expected.

At a rally with some 900 delegates, donors, Republican officials and supporters at a lakeside restaurant, Cruz barely mentioned Trump’s name during an appearance billed as a “thank you” event for supporters.

“Our party now has a nominee,” Cruz said Wednesday, just as Trump’s plane flew overhead. The senator laughed and turned his remarks toward the future, declining to say Trump’s name.

With an eye toward 2020, Cruz’s team drafted a convention speech focusing on adherence to the Constitution, a calling card for conservatives and a perceived contrast with Trump.

Texas fundraiser Mica Mosbacher said Wednesday that Cruz has taken a “quantum leap” with his convention speech after a rough primary, but based on conversations with his advisers the senator and his team are not ready to fully back Trump.

“I think they’re about 80 percent there,” said Mosbacher, who expects Cruz to make overtures toward unity in his remarks.

Paul Manafort, Trump’s top campaign adviser, said Wednesday that it will be clear from Cruz’s speech that he’s supporting Trump, though “how he says it, I don’t know.”

In a brief interview with The Associated Press, Manafort dismissed the importance of Cruz using the word endorse.

“No, it doesn’t at all. The point is the same… If he’s voting that’s the signal,” he said.

Before Trump even accepts the nomination, Cruz’s supporters as well as critics say undercurrents in Cleveland are emboldening the senator’s band of believers and stoking his 2020 prospects, should Trump lose in November.

Cruz is eager to be seen as the face of the modern conservative movement should Trump lose in November and create an open Republican field in four years.

So what Cruz says later Wednesday during his prime-time convention speech will be closely watched for clues about his presidential aspirations.

“I’m hopeful it’s a speech that rings so true and so motivating that we think of 1976 and Ronald Reagan,” said Iowa Rep. Steve King, a Cruz supporter. King was referring to Reagan’s words after losing the nomination to Gerald Ford only to win the presidency four years later.

Should Trump lose, King said of Cruz, the speech will be “the marker for him as front-runner” for 2020.

Cruz halted his campaign two months ago, having outlasted all but Trump in a field that once numbered 17 candidates. He finished a distant second in the delegate accumulation during the Republican nominating campaign.

Besides his prime-time speech, Cruz plans to address the Texas delegation Thursday.

Ron Kaufman, a Republican national committeeman from Massachusetts, said the flare-up over rules was choreographed to demonstrate public support for Cruz and preserve his future.

“These votes had nothing to do with Trump,” he said. “This is all about Ted Cruz trying to make the party smaller.”

By smaller, he meant that Cruz supporters were pushing for primaries where only registered Republicans can participate. Cruz was more successful in such contests than in ones also open to voters who aren’t registered Republicans.