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Ted Cruz’s non-endorsement speech not only drew Bronx cheers from Cleveland convention delegates who chanted “endorse Trump” throughout, but also is raising questions about whether it’s curtains for his political future – including a 2020 presidential run.

“I was disappointed when he didn’t endorse Trump,” Dallas delegate Mary Sue McCarty told FoxNews.com Thursday, on the sidelines of a rowdy breakfast session during which Cruz defended his decision.

“Cruz is someone who stands on principle but he doesn’t act on it. It’s political suicide,” McCarty said.

Cruz was no doubt reluctant to back the man he spent much of the primary campaign battling -- and he is widely reported to be preparing for another presidential run when the time is right, perhaps four years from now.

But in declining to align himself with this year's Republican nominee, he angered GOP stalwarts looking for party unity as the general election campaign against Hillary Clinton begins. The fallout could cause problems not only for another White House run, but his Senate re-election in two years.

A chorus of boos broke out after Cruz told the crowd to vote their conscience – a snub to Donald Trump less than 24 hours from his formal acceptance speech.

Speaking Thursday morning with Texas voters in Cleveland, Cruz faced a divided delegation demanding answers. Cruz stood by his choice.

“I am not in the habit of supporting people who have attacked my wife and attacked my father,” Cruz defiantly said.

The mood quickly soured as more and more delegates wanted to know why Cruz walked back on a pledge to support the eventual Republican nominee.

Cruz told the standing-room-only crowd that the pledge was “not a blanket commitment” and told an audience member that they “might have a similar view if someone were attacking your wife.”

McCarty believes Cruz is taking things too personally.

“In politics, you have to have skin like a rhino,” she said. “What about the picture that was released of Melania on the rug?”

She added: “You stood up and defended your wife and dad but it’s bigger than that now. It’s about the country. Your fellow Republican is not your enemy.”

Helen Gonzalez of Arlington, Texas, told FoxNews.com that she had been a Cruz supporter but his refusal to endorse Trump has made her reevaluate her support.

“I am very upset,” Gonzales said. “After this, I will never vote for Sen. Ted Cruz again.”

Rep. Jeb Hensarling, R-Texas, said he feels that Cruz "might have missed a two-foot putt."

"I thought he gave a great speech. I'm sorry he didn't quite get there at the end,” he told Fox Business Network.

Following Cruz’s speech Wednesday, another Texas delegate said he was disappointed in the senator.

“I’ll support Ted Cruz as a senator, but tonight we needed an endorsement to unify and move forward and we didn’t get that,” he told FoxNews.com. “We needed him. He’s a great conservative. He’s a great Texan. He’s a great speaker. He can unify just by giving an endorsement and he didn’t do that for us tonight.”

Former Republican vice presidential candidate Sarah Palin blasted Cruz on Twitter where she told him to “delete his career.”

In an interview with Brietbart News, Palin said, “Cruz's broken pledge to support the will of the people tonight was one of those career-ending 'read my lips' moments.”

But not everyone is ready to turn their back on Cruz.

Anne Mazone of Navasota, Texas, says with Cruz, what you see is what you get.

“There are more people that love him now,” Mazone told FoxNews.com. “That’s what we elected him for. Why do you expect him to be different now?”

A source close to Cruz's inner circle acknowledged to Fox News that the end of the speech "was tough, but sometimes standing for principle means getting booed."

"It's not classless to compliment Trump for winning," the source added. "It's not classless to highlight areas of policy where they can work together like border security, trade or fighting ISIS. It's not classless to call on all his supporters to not stay home, but turn out.”

Fox News' Cody Derespina and Fox Business Network's Blake Burman contributed to this report.