CLEVELAND (AP) — A day after being booed off the Republican National Convention stage, Texas Sen. Ted Cruz stubbornly defended his refusal to endorse Donald Trump, insisting he is not a “servile puppy dog” who would back anyone who personally attacks his family.

The blatant sign of GOP disunity angered some GOP delegates, former vice presidential candidate Sarah Palin, the Trump campaign and members of the nominee’s family. Trump’s son Eric called it “classless.” Even members of Cruz’s own Texas delegation confronted him at an appearance, with one voter shouting at the senator: “Get over it; this is politics!”

Trump had repeatedly mocked Cruz throughout the campaign as “Lyin’ Ted,” disparaged the appearance of Cruz’s wife, Heidi, and insinuated that Cruz’s father had indirect links to John F. Kennedy’s assassin, Lee Harvey Oswald.

Speaking to a passionate but divided Texas delegation, Cruz said the unconditional support for the GOP nominee that he had promised earlier this year disappeared “the day this became personal.”

“I’m not going to get into criticizing or attacking Donald Trump, but I’ll give you this response: I am not in the habit of supporting people who attack my wife and attack my father,” he said.

“And that pledge was not a blanket commitment that, if you go and slander and attack Heidi, that I’m going to nonetheless come like a servile puppy dog and say thank you very much for maligning my wife and my father,” he added.

Cruz tried to link arms with Republicans at the party’s national convention Wednesday but was booed lustily by delegates when he ended his speech without offering Trump his endorsement or even saying he would vote for the New York billionaire.

Cruz’ actions drew condemnation from Republicans, who questioned whether the senator had torpedoed his political future. His stand, however, could prove prescient depending on the outcome of the November election and the reaction of grass-roots GOP voters.

“He went back on his word to support the nominee. … Your word, in politics, has to be your bond. He’s politically dead,” said B J Van Gundy, a long time GOP activist in Georgia.

After Wednesday night, Cruz remerged Thursday morning to bring the Texas delegation to its feet at a downtown Cleveland hotel ballroom when he said he could have “turned tail and run, but that ain’t going to happen.”

And yet some in the Texas delegation, a majority of whom supported Cruz, angrily challenged the senator to publicly get behind Trump.

Soraya Zamora, a south Texas delegate, stood and pleaded with Cruz to rally behind Trump, pointing to his pledge to back the eventual nominee.

“I know that many things were said during the campaign, ugly things,” Zamora said. “However, I have to say it’s not about Donald Trump. It’s not even about Hillary Clinton. It’s about the United States of America.”

The sense of passionate conflict among Texans Thursday was a microcosm of the friction on the convention floor Wednesday night. Yet Cruz and his aides said he had submitted his speech to the Trump campaign for review in advance, and argued they knew it included no endorsement.

Cruz told his fellow Texans Thursday that, aside from overcoming the family attacks, he needed to see more from Trump’s policy agenda to sway him to vote for his former rival. The candidate has provided relatively few, and thin, policy proposals.

Reaction to Cruz was swift.

Former House Speaker John Boehner of Ohio, who had compared Cruz to the devil, responded by remarking: “Lucifer is back,” his spokesman said on Twitter. Former Alaska Gov. Sarah Palin, who had endorsed Trump, said in a Breitbart interview that Cruz’s move was a career-ender.

Although Trump tried to publicly brush off the struggle to win Cruz’s support, senior Trump adviser Paul Manafort went at Cruz’s pro-Constitution profile.

“Sen. Cruz, a strict constitutionalist, chose not to accept the strict terms of the pledge that he signed,” Manafort told reporters. “So as far as the contract was concerned, he was the one in violation, not anybody else.”

On Wednesday night, more than 2,000 delegates at the Quicken Loans Arena waited for Cruz to say something — anything — kind about Trump, but he demurred.

“And to those listening, please, don’t stay home in November,” Cruz said. “Stand and speak, and vote your conscience. Vote for candidates up and down the ticket who you trust to defend our freedom and to be faithful to the Constitution.”

The delegates responded with angry boos, and Cruz backer and former Virginia Attorney General Ken Cuccinelli escorted Heidi Cruz off the convention floor as she was heckled by Trump delegates.