Longtime conservative columnist George Will says he has left the Republican Party because of Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE.

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“This is not my party,” he said during a Friday speech to the Federalist Society, according to the conservative-leaning outlet PJ Media.

Will said he has switched his Maryland voter registration to "unaffiliated."

When asked in an interview later what message he had for GOP voters, Will suggested they resign themselves to not winning the presidency in November.

“Make sure he loses. Grit their teeth for four years and win the White House,” he said.

Will has been an outspoken critic of Trump, writing in a column in April that the presumptive GOP presidential nominee is imperiling Republican chances of maintaining its majority in the Senate.

“At least half a dozen Republican senators seeking reelection and Senate aspirants can hope to win if the person at the top of the Republican ticket loses their state by, say, only four points, but not if he loses by 10,” Will wrote.