Opinion | What Has Happened to My Party Haunts Me

With so much attention focused on the changes at the top of the Democratic ticket, we are not paying enough attention to the lack of change on the top of the Republican ticket. This month, Donald Trump won his party’s nomination for the third straight time. Whatever else we might say about him, he is a transformative figure.

This further confirmed, for me at least, the wisdom of my decision eight years ago to break with the Republican Party. In January 2016, I warned what were then my fellow Republicans that if they nominated Mr. Trump, he would constitute a grave threat to the nation. But I added that there was an additional reason to oppose him: Mr. Trump’s nomination would pose a profound danger to the Republican Party, in ways that Hillary Clinton never could. “For while Mrs. Clinton could inflict a defeat on the Republican Party, she could not redefine it,” I wrote. “But Mr. Trump, if he were the Republican nominee, would.”

And so he has. Few figures in American history have overhauled a political party as quickly and as fundamentally as Mr. Trump has. To understand just how different it is, we need to go back briefly to what it was like in the pre-Trump era.

During the time I served in three Republican administrations (Reagan and both Bushes), the party was hawkish and unrelentingly critical of the Soviet Union and then Russia. It was supportive of NATO. It condemned anti-American dictators and authoritarian leaders. It was deeply committed to “the common task of strengthening democracy throughout the world,” as Reagan said in 1982. And it argued that it was in America’s interest to provide global leadership.

The Republican Party championed free trade and fiscal discipline, though in practice it often fell short. It was welcoming of legal immigrants and refugees. Republicans argued that reforming entitlement programs was vital. Many of its leading figures insisted that moral character was an essential trait for political leaders and especially for presidents. Republicans warned, too, that a cruel, squalid political culture undermined a decent society.

Today, the Republican Party has jettisoned every one of these commitments.

Even on abortion, things have changed. The Republican Party has been pro-life for decades, including in its party plank. But this month that plank was removed. Princeton’s Robert P. George, a significant figure in the pro-life movement, pointed out that that plank has been replaced by the claim that abortion policy is entirely the business of states, which may, if they wish, permit abortion up to birth. Mr. Trump succeeded in overturning Roe v. Wade, but now that the abortion issue is a political liability, he has thrown the “pro-life cause under the bus,” Mr. George wrote on Facebook. Mr. Trump has succeeded where liberal Republicans long failed.