Henry M. Paulson Jr. is chairman of the Paulson Institute and a former U.S. treasury secretary and chief executive of Goldman Sachs.

Republicans stand at a crossroads. With Donald Trump as the presumptive presidential nominee, we are witnessing a populist hijacking of one of the United States’ great political parties. The GOP, in putting Trump at the top of the ticket, is endorsing a brand of populism rooted in ignorance, prejudice, fear and isolationism. This troubles me deeply as a Republican, but it troubles me even more as an American. Enough is enough. It’s time to put country before party and say it together: Never Trump.

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