When you dance with the devil, the choreography can get awkward.

Sen. Ted Cruz (R-Tex.) last week made his latest appeal to the U.S. nativist fringe by naming Rep. Steve King (R-Iowa) as a national co-chairman of his presidential campaign. King, called a “courageous conservative” and “incredible leader” by Cruz, is the anti-immigrant hard-liner who spoke of Mexican immigrants having “calves the size of cantaloupes” and who was a prominent birther.

King raised questions about President Obama’s birth certificate, voiced doubts that Obama had been born in the United States, floated the idea that Obama’s birth announcement in Hawaiian newspapers may have been placed “by telegram from Kenya,” and alleged that Obama “was not raised with an American experience.”

So we’re entitled to savor some schadenfreude now as Cruz himself gets caught in the birther web. Donald Trump’s questioning of Cruz’s status as a natural-born American and, therefore, his eligibility to be president is rough justice. Cruz, like Trump, has stoked the fires of resentment and xenophobia, so it’s entirely fitting that he gets burned.

But however tempting it is, I’m not joining in the Cruz birtherism; it was wrong when done to Obama, and it’s wrong now done to Cruz. Cruz, I am convinced, would make a truly awful president, but he is perfectly eligible to serve.

Rep. Alan Grayson, a Democratic gadfly running for the Senate in Florida, vows to file a lawsuit challenging Cruz’s eligibility if he wins the nomination. Grayson would try to argue that both parents of Cruz, who was born in Canada to an American mother and a Cuban father, had to be U.S. citizens for Cruz to be considered a “natural born” citizen under the Constitution. Grayson also has questions about the U.S. birth of Cruz’s mother. “The Obama birthers are loons,” Grayson told U.S. News & World Report. But “there’s a very good legal argument that Ted Cruz is not qualified to be president.”

Like Cruz foe John McCain (the 2008 Republican presidential nominee said Cruz’s eligibility is a “legitimate question”), Democratic leaders have been happy to see Cruz twist in the wind. “I do think there is a distinction between John McCain being born to a family serving our country in Panama and someone born in another country,” House Democratic leader Nancy Pelosi (Calif.) said Thursday.

But that’s not really so. My friend Neal Katyal, who was Obama’s acting solicitor general, joined Paul Clement, a Bush solicitor general, in a Harvard Law Review piece last year arguing that it’s not even a close call: The constitutional evidence back to the founding makes clear that “an individual born to a U.S. citizen parent — whether in California or Canada or the Canal Zone — is a U.S. citizen from birth and is fully eligible to serve as president.”

Attempting to argue the contrary leads to embracing dubious and anachronistic premises such as the long-abandoned notion that children of American fathers overseas are natural-born citizens but children of American mothers are not.

More broadly: Do Democrats and liberals and all those who howled about the injustice and the outrage of Obama’s birtherism really want to join the cause of Cruz birtherism, simply because he’s a Republican, or a conservative? No doubt it would be satisfying to give conservatives a taste of their own medicine, but that would mean embracing the nativism that is turning the Republican Party into a fraternity of old white men from rural areas. The right is uniquely ill-behaved these days. Why join it?

It wasn’t always this way. In the early days of the Obama presidency, I argued that the left was more ill-tempered. But now there’s nothing equivalent to the right’s rage — despite attempts to draw some phony parallels.

When I wrote about the overt racism injected into the campaign by Trump, the 2016 front-runner, conservative critics countered by citing the history of race-baiting by the Rev. Al Sharpton, a minor Democratic candidate in the 2004 race. When I wrote about Republican officeholders’ support for the armed men who took over a U.S. government facility in Oregon, conservatives argued that this was no different from Obama’s tolerance of “sanctuary cities” — though sanctuary policies have existed for decades without successful legal challenges.

Then there’s the birther movement, led by Trump, which sought to portray the first African American president as a foreigner. Now Trump is, with his characteristic disregard for truth, attempting to turn the same nativist forces against his nearest competitor in the Republican primary.

There is no equivalent on the left these days to such nasty stuff. Democrats should keep it that way.

Twitter: @Milbank

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