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SAN ANTONIO (CBSDFW.COM/AP) — A border patrol union has backed out of a meeting with Republican presidential candidate Donald Trump, but the billionaire businessman is charging ahead with plans to visit the U.S. Mexico border Thursday as part of a high-profile trip that promises new challenges for the GOP’s years-in-the-making push to attract Hispanic voters.

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After the National Border Patrol Council, Local 2455 canceled the meeting the Trump “Make America Great Again!” campaign issued a statement that said, in part, “they were totally silenced directly from superiors in Washington who do not want people to know how bad it is on the border — every bit as bad as Mr. Trump has been saying.”

Trump has gone beyond the party’s hardline stance on illegal immigration, calling immigrants who cross the border illegally “criminals” and “rapists” and accusing Mexico’s government of deliberately sending felons into the U.S. His trip Thursday also comes amid an escalating feud with Republican rivals and criticism from members of both parties, guaranteeing the billionaire developer plenty of attention from voters and reporters.

The reality television star is set to make multiple public appearances in Laredo, Texas, including at an afternoon news conference on the border. He also planned to meet members of the union that represents U.S. Customs and Border Patrol agents, although the union canceled the meeting hours before it was scheduled to begin.

“After careful consideration of all the factors involved in this event and communicating with members of the National Border Patrol Council … it has been decided by Local 2455 to pull out of all events involving Donald Trump,” union president Hector Garza said in a written statement issued Thursday morning, declining to elaborate on why the group canceled.

“Our intentions to meet with Mr. Trump was to provide a ‘boots-on-the-ground’ perspective to not only Mr. Trump but to the media that would be in attendance at this event,” Garza said.

From party heavyweights like former Florida Gov. Jeb Bush to relative newcomers to the national scene like Wisconsin Gov. Scott Walker and Ohio Gov. John Kasich, Trump’s rivals face his hair-trigger habit of calling out his critics by name, vilifying the GOP establishment and roiling the debate over immigration.

In Washington on Wednesday, former Texas Gov. Rick Perry was asked about Trump’s trip to Laredo. He snapped, “I hope he can find the border because I’m not sure he’s ever been there before.”

That was after Perry denounced Trump’s campaign as a “cancer on conservatism” and a “barking carnival act” in a speech that defined “Trumpism” as “a toxic mix of demagoguery, mean-spiritedness and nonsense that will lead the Republican Party to perdition if pursued.”

Indeed, the insults flying between Trump and his rivals have been caustic. Sen. Lindsey Graham, R-S.C., said Thursday, “The only way we’re going to be able to lose the election is continue to say things like Donald Trump is saying.”

“Donald Trump is a great showman,” Graham said in an appearance on a cable news network program. ”That’s why all these companies hired him to sell their products. That’s the reason all these companies are firing him, because he’s toxic.”

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“I think he’s sort of a political car wreck where people slow down and watch,” Graham added.

Others in the GOP field have been more measured, though showing signs of growing exasperation. Bush, in particular, has conspicuously tried to avoid alienating Trump’s supporters — “good people” with “legitimate concerns” — even while branding Trump’s rhetoric as “ugly” and “mean-spirited.”

The feud is unfolding as the candidates head into a presidential election in which Hispanic voters will play a critical role, particularly in swing states like Nevada, Colorado and Florida.

“If Hispanic Americans perceive that a GOP nominee or candidate does not want them in the United States, they will not pay attention to our next sentence,” reads a Republican National Committee report released after the 2012 election citing the need to embrace Hispanic voters. “It does not matter what we say about education, jobs or the economy; if Hispanics think we do not want them here, they will close their ears to our policies.”

Yet Trump, who has become a dominant force in the 2016 contest, has clearly stated, over and over again, that Mexican immigrants are unwelcome.

“The Mexican government is forcing their most unwanted people into the United States,” and “criminals, drug dealers, rapists” are among them, he said in a recent statement that also declared “great respect for Mexico.”

Another candidate for the nomination, Sen. Rand Paul, R-Ky., earlier in the week addressed the Trump feud almost serenely, expressing confidence the primary campaign would “get beyond the novelty of a reality TV star.”

Walker, campaigning in Tennessee, said he used to run track and “I realized there were some folks sprinting out ahead. I made sure I was ahead at the end of the race when it really mattered.”

Florida Sen. Marco Rubio likened Trump to Barack Obama, whom he called a president with “no class” and one who demeaned the office with his appearance this week on Comedy Central’s “The Daily Show.”

On Fox News, Rubio said of Trump: “I don’t think the way he has behaved over the past few weeks is either dignified or worthy of the office he seeks.”

Trump remained unbowed. “I’m called a jackass,” he said Wednesday on CNN. “You have to fight back. The country has to fight back. Everyone’s pushing our country around. We can’t allow that.”

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