CLEVELAND — Ted Cruz has been here before, but maybe never like this.

After upending Donald Trump's Republican National Convention with his conspicuous non-endorsement of the presidential nominee, Cruz is confronting isolation and unease in his home-state GOP, which has largely been moving toward Trump even as he continues to withhold support.

"The isolation is increasingly rapid, and it seems to me only the most fervent Ted Cruz supporters are hanging on," said Carl Tepper, former president of the Texas Republican County Chairmen's Association and an at-large delegate from Lubbock.

More than 36 hours after Cruz left the stage in Cleveland amid thunderous boos, very few prominent Texas Republicans were rushing to his defense. In fact, more could be seen and heard bluntly voicing disagreement with the attitude Cruz took toward his party's presidential nominee.

"It was just painful. It was not what I would consider what we needed at a convention," state Sen. Charles Perry of Lubbock said in an interview Thursday on Lubbock radio.

"He had an opportunity ... in my opinion, to unify, probably more than anyone else in that convention, bringing people together, and I think he missed that opportunity," added Perry, who was an endorser of Cruz's bid for the White House.

Such frustrations with Cruz seemed to boil over Thursday morning here at the Republican National Convention, where Cruz faced a hostile crowd at his own state's delegation breakfast. Members of the audience pressed him — often angrily — over his refusal to back Trump and he gave no ground, further infuriating some delegates.

Read More Ted Cruz Takes Heat from Texas Republican Delegates

Of course, it is not the first time the polarizing Cruz has rubbed fellow Republicans, even some in his home state, the wrong way. Yet the dispute at hand looks to be more intense and prolonged than prior disagreements, with Cruz showing no signs of coming around to Trump even as the pressure from within his own ranks reaches a new high.

The intra-party discord comes as Cruz charts a political future that depends on, at a minimum, winning re-election two years from now. Up until the convention, the idea that a fellow Republican could credibly challenge Cruz in 2018 largely evoked blank stares.

After the breakfast Thursday, one top county party official said Cruz's non-support for Trump was "already haunting him" as the 2018 race takes shape.

"I will never support him for anything" again, said Anna Maria Farias, vice chairman of the Bexar County GOP. "We made calls for him when he was running in the primaries. That will not happen again."

Speaking with reporters after Cruz's appearance at the breakfast, former campaign manager Jeff Roe said "of course there could be" political ramifications for Cruz's re-election bid following his controversial showing in Cleveland.

"If you want to measure this on the political expediency chart, this is off the charts the other way," Roe told reporters. "If this were all for politics, none of this would've happened."

“ Ted's got time to get right on this deal, and I hope he will. ” — Former Texas Gov. Rick Perry on Fox Business Network

Asked about the prospect of a primary challenge in 2018, Roe deployed a timeworn adage of re-election campaigns.

"You either run scared or unopposed, so we're always running scared," he told reporters.

Perhaps most revealing after Cruz's speech, though, was the relative silence from Lt. Gov. Dan Patrick, a fellow star in Texas Tea Party circles who supported Cruz in the primaries and now enthusiastically backs Trump. Patrick — who spent the first three days of the convention racing around Cleveland for media appearances, preaching party unity — was conspicuously subdued Thursday morning.

In Roe's telling, Patrick was among the last people Cruz spoke with before he took the stage Thursday night, when pro-Trump forces waged a last-minute effort to get Cruz to make his speech more supportive of the nominee. It is not known what Cruz and Patrick discussed, but if his remarks to the Texas delegation the next morning were any indication, he was less than thrilled with how Cruz's address turned out.

"I was chair of Ted's campaign [in Texas] and was proud to be chair of Ted's campaign, but as I said yesterday, I want to defeat Hillary Clinton, I'm supporting Donald Trump and I hope we unify," Patrick said. "I believe that is my conscience."

It was not long after Cruz's speech before Trump allies were floating Patrick as a potential challenger to Cruz in 2018. Patrick has previously said he plans to run for re-election as lieutenant governor that year and is not eying any other office.

On Friday, an ally of Patrick, state Sen. Paul Bettencourt of Houston, issued a statement in response to "any endorsement controversies" that urged Texas Republicans to vote a straight GOP ticket in November "from the White House down to the courthouse." The choice between the two parties is "obvious," said Bettencourt, the chairman of the Senate GOP caucus.

Gov. Greg Abbott had no comment Thursday on Cruz' speech, according to an Abbott spokesman. Abbott was forced to skip the convention due to burns he suffered earlier this month on a family vacation. He asked Patrick to replace him as chairman of the Texas delegation.

A number of Cruz's Republican colleagues in the Texas congressional delegation were keeping their distance as well. U.S. Rep. Bill Flores of Bryan took a pass Thursday on saying whether Cruz's speech hurt the GOP unification process, saying it's "up for the people of Texas to decide — about how they feel about what he said and the impact that it has on his political future."

Other Texas Republicans were more explicit in their assessments of Cruz's political standing after his convention speech. They included U.S. Rep. Pete Sessions of Dallas, who supported Jeb Bush in the primary and endorsed Trump shortly after he became the presumptive nominee.

Speaking with reporters Thursday, Sessions suggested Cruz was part of a group of "people that want to go play their own way, go sit in the corner and suck their own thumb."

"People that want to pick on Donald Trump and Mike Pence — I do take that personally," said Sessions, who was close to Pence when he served in Congress. "I do take it personally that they are making themselves the issues rather than purity, rather than the good of the whole."

There is still time for Cruz to see the light, according to one Texas Republican with ample experience in having a change of heart on Trump: Rick Perry. The former governor was the first presidential candidate to seriously attack Trump, once calling him a "cancer on conservatism," but came around shortly after Trump became the presumptive nominee.

"He made a mistake," Perry, a former Cruz supporter, said Thursday on Fox Business Network. "Ted's got time to get right on this deal, and I hope he will."

The likelihood of such a reversal from Cruz appeared to dim Friday, as Trump proclaimed during a boisterous speech to supporters that he wouldn't even accept an endorsement from Cruz at this point. Trump also took care to note that by the end of Cruz's convention speech, "there wasn't a person in the room who wasn't" booing.

"Including," Trump added, "the Texas delegation."