The other thread that Trump pulls is more political: what we now call McCarthyism, although it, too, goes back to our nation’s earliest days. It vilifies opponents as enemies of the state.

More than two centuries ago, opponents of Thomas Jefferson warned that he was a Jacobin who if elected would unleash a French-style reign of terror upon America. As one commentator put it, “The Bible would be cast into a bonfire, our holy worship changed into a dance of Jacobin phrensy, our wives and daughters dishonored.” Senator Joseph McCarthy updated that in the 20th century with reckless accusations that leftists were Communists — and now Trump picks up that mantle by suggesting that his four progressive targets in Congress “might be” Communists, not to mention that they “hate our Country” and are “pro Al-Qaeda.”

I’m not sure whether this new McCarthyism is instinctive and unthinking, or these bilious rants represent a shrewd effort to manipulate voters into seeing the 2020 presidential campaign through the prism not of issues but of racial identity, in hopes of winning Trump an edge with white voters.

I do know that Trump has taken two of the most ignominious threads in American history — nativism and McCarthyism — and woven them together in an outburst that is an affront to democratic norms.

If anyone doubts that Trump’s statements were despicable, note that the U.S. Equal Employment Opportunity Commission specifically bars employers from using “ethnic epithets, such as making fun of a person’s foreign accent or comments like, ‘Go back to where you came from.’”

Frankly, I’m even more troubled by Trump’s policies than by his tweets, and I wish the reaction to Trump focused more on practical initiatives to reduce child poverty, treat drug addiction or end mass incarceration. But the question put to Congress this week was a resolution properly condemning the presidential tirade. It was grotesque to see Republicans who had been mute at presidential bigotry suddenly protest that the backers of the resolution violated rules of decorum.

Really? We’re left again with the question: How can members of the party of Lincoln today protest the label of racism, but not the racism itself — in a man who for 45 years has shown himself to be a racist from his mandible to his metatarsals?

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