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• Photographer, Secret Service agent tussle at Trump rally

  The day of Donald Trump’s greatest electoral triumph was disturbed by the creaking sound of a breaking coalition — with more traditional Republicans talking about bolting.

  One congressman said he’d never vote for Trump; a senator said he’d leave the party first; a well-known conservative writer suggested joining a third party; and a Trump ally accused elites of planning to gang up and steal the nomination through procedural chicanery.

  READ MORE: Super Tuesday: Could Republican party split over Trump?

  The day ended with Trump winning most states. In a jubilant meeting with reporters, he vowed to unify the party, and expand its blue-collar appeal. But the day had begun with one of the most conservative people in Congress declaring he might leave it.

  “The Republican party is just a tool — as all political parties are,” Nebraska Sen. Ben Sasse told MSNBC’s Morning Joe program.

  “I signed up for the party of Abraham Lincoln — not the party of David Duke and Donald Trump… If the Republican party becomes the party of David Duke and Donald Trump, I’m out. And I think lots, and lots, and lots of people are out.”

  Sasse is rated as the sixth-staunchest conservative in Congress by the Heritage Action group. But the final straw for him appeared not to be Trump’s ideological ping-pong where he bounces around between policies linked more by economic and cultural angst than by any cohesive conservatism.

  WATCH: Donald Trump covers a variety of topics while speaking to supporters in Florida on Super Tuesday.

  ‘Mexico is going to pay 100 per cent’: Trump on Mexican border wall

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  ‘Mexico is going to pay 100 per cent’: Trump on Mexican border wall

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  Trump disavows endorsement from KKK supporter David Duke

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  Trump says US media declared Rubio ‘big loser of the night’

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  Trump defends Planned Parenthood but says he won’t fund abortions

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  Trump says that he has expanded the Republican party

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  Trump says companies moving out of New Jersey, Christie shakes head mouthing ‘no’

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  Trump says that he is going to beat Rubio in his home state of Florida

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  Trump makes victory speech after winning several states on Super Tuesday

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  Chris Christie says Donald Trump is a movement, bringing America together

  
  
  

  An example of his uniquely Trumpian platform came at a rally Tuesday. Trump threatened to slap a 35-per-cent import tax on an air-conditioning company that shipped jobs to Mexico — this while campaigning to lead a party that hates taxes; supposedly supports free trade; and professes abhorrence for presidential imperialism.

  No, the final straw appeared to be Trump receiving the explicit support of America’s most famous Ku Klux Klansman — and Trump’s coy routine over whether to disavow Duke. He actually did so, but with an uncharacteristic degree of gentleness, compared to the avalanche of abuse he’s poured onto others.

  READ MORE: Racial feud erupts as Republicans fight ‘unstoppable’ Trump

  Trump addressed it again Tuesday night: “I disavowed,” he said, referring obliquely to Duke. “I mean, how many times are you supposed to disavow?”

  This episode has popped the boil discreetly bubbling within the Republican party in recent months, as the prospect of a Trump nomination shifted from the realm of Washington cocktail-party ridicule to real-world likelihood.

  WATCH: Political scientist Dr. Robert Murray explains how the Donald Trump campaign has turn the U.S. presidential race upside down and damaged the Republican party.

  One lawmaker issued a statement: “My love for our country eclipses my loyalty to our party, and to live with a clear conscience, I will not support a nominee so lacking in the judgment, temperament and character needed to be our nation’s commander-in-chief,” Scott Rigell of Virginia said in an email.

  “If left with no alternative, I will not support Trump in the general election should he become our Republican nominee.”

  Trump has less than one-third of the delegates he needs to seal up the nomination. But given his polling lead there could be only two ways Republicans can stop him now: One is a sudden, mass movement toward another candidate — which was complicated Tuesday as everyone else vowed to keep campaigning.

  The messier option would be to somehow limit his delegate count to less than a 50-per-cent-plus-one majority, then at the summer convention strip him of the nomination on the second ballot.

  An old Trump ally suspects that’s the plan. Roger Stone wrote a piece accusing his opponents of planning to collude with each other, and agree on a second-ballot alternative to Trump.

  “Beware Republicans: the big steal is coming,” his longtime adviser wrote in a piece on the Trump-friendly site Breitbart. “The DC-Wall Street cabal that has dominated the GOP since 1988 has no intention of letting the billionaire real estate mogul be nominated.”

  Another well-known conservative writer floated a different option: Conservatives jump ship en masse, take over a small outfit like the Constitution party, and run a more acceptable candidate.

  “It is time for Republicans to seriously consider an exit strategy as they grapple with the rise of Trump,” Erick Erickson wrote.

  “It may be necessary for men and women of principle within the party to set the self-detonation sequence as they escape the ship to a new party. Trump and his angry band of supporters are starting to board and the GOP, as an entity, will be a terrible place to stay for many elected officials.”

  These schemes would not only be difficult — but extremely risky.

  The potential exists for an explosive grassroots reaction. As detested as he is in the corridors of official Washington, a majority of Republicans tell pollsters they’d support Trump.

  Trump was asked Tuesday night about the scenario of a secret Plan B to take him out: “We’re a democracy,” he said. “I think it’s awfully hard to say, ‘That’s not the person we want to lead the party.’”

  WATCH: Protesters interrupted Donald Trump’s rally on Tuesday several times. Trump shouted at them from the stage, “out, out, out.” He told the roaring crowd that the protesters wouldn’t be there if the nation wasn’t so politically correct.