In a new TV ad, a sitting Republican congressman is explicitly running against the man leading his party's ticket.

"I'm a Marine — for me, country comes first," said Representative Mike Coffman of Colorado in a new commercial released on Thursday. "My duty is always to you. So if Donald Trump is the president, I'll stand up to him. Plain and simple."

Yes, that's the same Mike Coffman who peddled Trump-style birtherism four years ago and got into hot water when he said, "I don't know whether Barack Obama was born in the United States of America."

"I don't know that," Coffman said of the president at a fundraiser. "But I do know this, that in his heart, he's not an American. He's just not an American."

Coffman later profusely apologized on camera when it became clear that birtherism was on its way out, and after his formerly hardcore Republican district was redrawn to include a more moderate constituency.

But that was then: Now, Coffman is positioning himself as an openly anti-Trump Republican. He even recorded a version of the new ad in which he speaks Spanish.

The TV spot was released only a few days after Coffman told the New York Times that he disapproved of Trump's attacks on the family of Humayun Khan, a Muslim-American soldier who died in Iraq.

"Having served in Iraq, I'm deeply offended when Donald Trump fails to honor the sacrifices of all of our brave soldiers who were lost in that war," Coffman said.

Plenty of other Republicans quietly oppose Trump, but Coffman joins the club formerly made up of only one GOPer, Senator Mark Kirk of Illinois. Unlike Coffman, Kirk is a pro-choice moderate who, while registered to the party, touted his "independent" voice in running for Senate.

"Mark Kirk bucked his party to say Donald Trump is not fit to be commander-in-chief," Kirk's ad said.

The ad is yet another defection facing Trump this week after eBay founder and longtime Republican Meg Whitman made headlines for endorsing Hillary Clinton, and Trump himself stirred the pot within his own party by refusing to endorse House Speaker Paul Ryan and Senator John McCain, who are both up for re-election.

Follow Brendan James on Twitter: @deep_beige

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