A former state chairman for Sen. Ted CruzRafael (Ted) Edward CruzIn partisan slugfest, can Chip Roy overcome Trump troubles? Cruz: Hunter Biden attacks don't move 'a single voter' GOP clears key hurdle on Barrett's Supreme Court nomination, setting up Monday confirmation MORE's (R-Texas) presidential campaign is calling for an "insurrection" at the Republican National Convention this summer to keep Donald TrumpDonald John TrumpGiuliani goes off on Fox Business host after she compares him to Christopher Steele Trump looks to shore up support in Nebraska NYT: Trump had 7 million in debt mostly tied to Chicago project forgiven MORE from being nominated.

"There's a moral obligation for the delegates in that convention to nominate the best candidate to beat Hillary ClintonHillary Diane Rodham ClintonGorsuch rejects Minnesota Republican's request to delay House race Biden leads Trump by 6 points in Nevada: poll The Memo: Women could cost Trump reelection MORE. It's clearly not Donald Trump," Steve Lonegan, Cruz's New Jersey state chairman, said on CNN's "At This Hour."

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"These delegates have an obligation on day one — I don't care about being bound on the first ballot. Break the rules, unbind yourself. This guy's gonna lose, he's going to take the Republican Party down to cataclysmic defeat," he added.

Lonegan is a spokesman for the Courageous Conservatives PAC.

Lonegan said ever since Cruz dropped out in early May, "I've woken up every morning looking for reasons to support Donald Trump, and it's going in the other direction."

Republicans leaders have broadly started to coalesce around Trump since his last GOP rivals dropped out of the race, though the businessman has sparked condemnation for racially charged remarks in recent days going after the Mexican heritage of a federal judge overseeing lawsuits against Trump University.