Tomorrow is Cinco de Mayo, celebrating Mexican traditions, and I’d like to start the festivities early with a pop quiz. Who suggested erecting “a brass wall around the country?”

Donald Trump, 2015? Nope. Try John Jay, the first chief justice of the U.S. Supreme Court, in the 1750s. Jay was determined to keep out those dangerous Catholics.

Sadly, fear and hatred of immigrants is as American as apple pie, pizza and tacos. The current target of this bigotry is Mexicans here illegally. Years ago it was Italians, Jews and other “undesirables.” “No Irish Need Apply!” was a common warning on job and housing notices. The Johnson-Reed Act of 1924 barred Asians from entering the United States.

Unscrupulous politicians past and present love to play on our fears.

As usual, it’s based on lies. Unauthorized Mexican immigration is declining, and Mexican immigrants don’t commit more crimes. According to The Washington Post, data show newer immigrants — including those here illegally — are less likely to commit crime.

But in troubling economic times, politicians too often demonize “the other.” Trump promises to build a huge wall on the Mexican border to keep “them” out, while Sen. Ted Cruz threatens to increase deportation.

You say you really don’t know any Mexican-Americans? How about Demi Lovato and Eva Longoria? What about Hilda Solis, who served as U.S. secretary of labor under President Barack Obama, or Bill Richardson, former governor of New Mexico who negotiated the release of American prisoners in Iraq and North Korea?

Still, Mexicans continue to be demonized. I recently visited the Tenement Museum on the Lower East Side (don’t miss it), and was reminded the nation was built on the backs of immigrants. Their energy and inspiration continue to make us a great nation.

It’s time to break the cycle. Show political demagogues trying to appeal to our worst instincts that we know they’re the same types who stirred up hatred against many of our own ancestors. Hardworking Mexican immigrants aren’t a threat to the American way. Political demagogues are.

Meanwhile, happy Cinco de Mayo!

Playwright Mike Vogel blogs at newyorkgritty.net.