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Is Marco Rubio taking back his pledge to support the GOP nominee?

That’s the question being raised after the Florida senator gave a muted response this morning to the possibility of Donald Trump winning the nomination.

Asked whether he would get behind Trump if the billionaire businessman is selected, Rubio answered, “I don’t know.”

His uncertainty marks a contrast from the earlier vow Republican candidates took to support the party nominee.

Rubio’s camp has not been shy about denying Trump a win, even recently beginning to urge supporters to vote for Ohio Gov. John Kasich in the upcoming Buckeye State primary, Peter Doocy noted on Fox and Friends Weekend.

Rebecca Berg of Real Clear Politics later said that Rubio is trailing Trump by double digits in his home state, though the senator hopes to make up for the gap with early voters and minorities.

Rubio "looked exhausted emotionally," in his earlier comments, she said on Cost of Freedom.

Watch more, above.

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