A former state chairman for Sen. Ted CruzRafael (Ted) Edward Cruz228 Republican lawmakers urge Supreme Court to overrule Roe v. Wade GOP, Democrats battle over masks in House, Senate Human rights can't be a sacrificial lamb for climate action MORE's (R-Texas) presidential campaign is calling for an "insurrection" at the Republican National Convention this summer to keep Donald TrumpDonald TrumpMeghan McCain: Democrats 'should give a little credit' to Trump for COVID-19 vaccine Trump testing czar warns lockdowns may be on table if people don't get vaccinated Overnight Health Care: CDC details Massachusetts outbreak that sparked mask update | White House says national vaccine mandate 'not under consideration at this time' 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 ClintonClintons, Stacey Abrams meeting Texas Democrats Biden says Russia spreading misinformation ahead of 2022 elections Highest-ranking GOP assemblyman in WI against another audit of 2020 vote 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.