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A day after showcasing Republican unity, President Trump is warning a GOP Senator about new attacks.

FOX's Jared Halpern has more from Capitol Hill:

Arizona Senator John McCain warned against half-baked, spurious nationalism in a speech last night, this morning telling reporters his remarks are not specifically aimed at President Trump:

(McCain) "I was referring to the whole atmosphere and environment around here. This idea that quote America firsters."

In a radio interview, President Trump warned, at some point, he would fight back and it won't be pretty.

McCain response: that's fine, saying he's faced some fairly significant adversaries in the past.

On Capitol Hill, Jared Halpern, FOX News.

Follow Jared Halpern on Twitter: @JaredHalpern