WATCH: Republican Senator Mark Kirk Attacks Donald Trump in TV Ad

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Senator Mark Kirk, who is running for reelection in Illinois, has become the only Republican to attack Donald Trump in a campaign ad.

In a new advertisement entitled “Even More,” Kirk touts the fact that he was the first Republican to withdraw his support for Donald Trump.

“Mark Kirk bucked his party to say Donald Trump is not fit to be commander in chief,” the ad says.

The commercial overall is focused on Kirk’s history of breaking from his own party, as it also mentions that he is pro-choice and that he supports meeting with Merrick Garland, President Obama’s Supreme Court nominee.

Kirk rescinded his endorsement of Trump earlier this month in direct response to the New York businessman’s comments about Judge Gonzalo Curio. The Illinois senator is in the midst of a tough reelection fight, and Politico has said he is the most vulnerable Republican senator on the ballot in 2016.

The senator is clearly hoping that embracing his independent record will help him in Illinois, a traditionally blue state. But while we have previously seen Republican politicians abandoning Trump, never have we seen someone actively campaigning on that fact before now.