Former Rep. Vin Weber said he wouldn't vote for Donald Trump. | Getty Gingrich ally: Trump nomination 'a mistake of historic proportions'

A former Republican congressman said Wednesday that Donald Trump’s nomination was “a mistake of historic proportions" for the Republican Party.

Vin Weber, who represented Minnesota in the House of Representatives for 12 years and worked closely with Newt Gingrich, told CNBC on Wednesday that he would not vote for Trump in November. Gingrich is supporting Trump and was considered a frontrunner to be his running mate.


"I won't vote for Trump," he said. "I can't imagine I'd remain a Republican if he becomes president."

Weber said he has not decided whether he would vote for Hillary Clinton, the Democratic nominee, but he said the world would be “all in shambles” if Trump is elected. He blasted Trump’s position on trade and said he is worried about the survival of the Republican Party with Trump as its leader.

He added that he understood why Paul Ryan and other Republican leaders have endorsed Trump, but he said he would applaud Republican leaders who reject his candidacy.

Weber joins a growing list of notable Republicans who have recently said they will not support Trump's candidacy, including HP CEO Meg Whitman, Sally Bradshaw, a longtime aide to Jeb Bush, and Maria Comella, a former top aide to New Jersey Gov. Chris Christie.

Gingrich himself suggested earlier Wednesday that Trump has engaged in "very self-destructive behavior" of late and needs to "discipline himself." In another interview with The Washington Post, the former House speaker remarked that "Trump is helping [Clinton] to win by proving he is more unacceptable than she is.”