Republican presidential candidate Donald Trump addresses the Sunshine Summit in Orlando last week. (John Raoux/Associated Press)

“OUR PRESIDENT wants to take in 250,000 from Syria,” says Donald Trump, falsely. “Think of it, 250,000 people. And we all have heart, and we all want people taken care of and all of that, but with the problems our country has, to take in 250,000 people — some of whom are going to have problems, big problems — is just insane.”

It is not insane. It is a lie. It is a lie that Mr. Trump repeats, even as fact checkers and reporters point out that it is wrong. Not just repeats, but embellishes. Last month, the number was lower: “Now I hear we want to take in 200,000,” he said on ABC News. “We don’t know where they’re coming from. We don’t know who they are. They could be ISIS. It could be the great Trojan horse.”

We have grown accustomed to politicians exaggerating, sometimes stretching the truth, sometimes fogging it up for effect. But it is disturbing on a different scale to see a U.S. politician repeating a big lie again and again, in a way that is calculated to inflame bigotry and fan fears.

Here are the facts: President Obama wants to allow 10,000 Syrian refugees into the country next year. The number may increase a bit the year after that, but it will be nowhere close to 200,000 or 250,000. So far, over the course of a four-year civil war, the United States has accepted fewer than 2,000 Syrian refugees, and the screening process for each prospective admission can take up to 18 months.

To the extent it has any connection to reality, Mr. Trump’s number appears to reflect the total number of refugees, from all over the planet, that the United States may accept over the next three years. Mr. Obama wants to increase the country’s take from between 70,000 and 80,000 people annually to 100,000 in 2017. Some of the additional refugees would come from Syria. Many others would be fleeing desperate conditions in Africa and other dangerous corners of the world.

After the Paris attacks, it’s understandable that Americans ask questions about the quality of U.S. refugee screening. But the discussion must be based on reality, not phantoms. The risk from a small number of vetted refugees is far outweighed by the humanitarian imperative to help innocent people escaping from Syria’s evil rulers and from the Islamic State.

Mr. Trump is fanning hysteria in other ways. Whereas the integration of Muslims in U.S. society, including in the armed forces, is a success story compared with Europe, the businessman would have us believe the opposite.

“The hatred is beyond belief,” Donald Trump said Monday, as he talked about surveilling and even shuttering mosques. “The hatred is greater than anybody understands.”

We continue to have enough faith in voters to believe that Mr. Trump won’t wind up in the White House. But he can still promote misconceptions that pull his party down, sully the post-Paris policy debate and, ultimately, hurt innocent people. Given his serial refusal to accede to reality, we doubt he will agree. The rest of his party must do better.