Donald J. “Smart Person” Trump keeps stepping in it.

The president-elect told Fox News Sunday that he doesn’t feel obligated to follow what’s known around the world as a “One China Policy.”

It’s a simple concept.

The People’s Republic of China says there is only “one China.” Taiwan, which calls itself the Republic of China on Taiwan, also says there is just a single China.

Neither country recognizes the other diplomatically. Taipei has no PRC embassy, Beijing has no Taiwanese embassy. Almost the entire rest of the world recognizes the PRC as the sole China. The United States of America has recognized the PRC since 1979, at which time it ended relations with Taiwan.

Now we have the president-elect of the  United States saying he isn’t bound to follow a One China Policy. Trump told Chris Wallace on Fox News Sunday: “I don’t know why we have to be bound by a One China policy unless we make a deal with China having to do with other things,” he said. This is ridiculous on its face.

The communists who now govern the PRC took the country by brute force in a civil war that erupted after World War II. The nationalist Kuomintang party, which governed China under the rule of Chiang Kai-shek, fled to Taiwan in 1949 and set up a government in exile.

China declared Taiwan to be a “renegade province” and vowed to take it back, by force if necessary. The world for decades didn’t recognize the PRC as the legitimate Chinese government; it gave that recognition to Taiwan.

President Nixon changed all of that by going to China in 1972, shaking hands with Mao Tse-Tung and giving birth to a new bilateral relationship. President Carter sealed the deal in 1979 by offering diplomatic status to the PRC.

“Smart Person” Trump, though, decided to roil the waters by speaking over the phone with Taiwanese President Tsai Ing-wen, who had called to congratulate him for being elected president. The PRC is damn angry! They have expressed “serious concern” over that breach of protocol.

Meanwhile, some Republican hardliners at home are cheering the president-elect for this outreach.

There is a crystal-clear reason why Taiwan doesn’t just declare its independence from the PRC and, thus, set up a de facto second China. Some officials expressed it to me during my first visit in 1989 to the island nation. “We take these threats” of military retaliation by the PRC if Taiwan declares its independence “very seriously,” they said.

And they should. The PRC possesses a gigantic military apparatus — in addition to its enormous economic impact around the world.

Taiwan functions as an independent nation. It has trade relations with many countries around the world. The United States is sworn to defend Taiwan in the event of an attack by the PRC. It does not belong, though, to the United Nations or to the World Health Organization. It has been shut out of virtually all worldwide cooperative agreements.

If there ever is to be anything other than a One China Policy enacted, that has to come from Beijing and Taipei. Those two nations have to reach an agreement of some sort that recognizes that Taiwan never will be assimilated back into the mainland.

Will that happen? Taiwanese officials believe to this day that their future remains on the mainland. They are intent on waiting for the communist system to fail in Beijing, just as it failed in Moscow. That might be a pipe dream, but it is their dream.

The president of the United States needs to butt out.

A smart person knows at least that much.