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Mitt Romney announced on Facebook that he's backing Ted Cruz in Utah's Republican caucus, saying that Cruz winning state contests is the only path to an open convention in which a Republican other than Donald Trump can win the nomination.

The 2012 Republican nominee also said that there's a contest between "Trumpism" and Republicanism.

"Through the calculated statements of its leader, Trumpism has become associated with racism, misogyny, bigotry, xenophobia, vulgarity and, most recently, threats and violence. I am repulsed by each and every one of these.

"The only path that remains to nominate a Republican rather than Mr. Trump is to have an open convention. At this stage, the only way we can reach an open convention is for Senator Cruz to be successful in as many of the remaining nominating elections as possible.

The former Massachusetts governor also said that he likes John Kasich, but that a vote for him only increases Trump's chances of locking down the nomination.

Trump fired back on Twitter, calling Romney a "mixed up man" and said that him backing Cruz is good for the billionaire businessman.

Watch Trace Gallagher's report on "Your World" below.

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