Monday was Parson Weems Day. This is my designation to mark the voting in Iowa as the end of the first lying season. The Rev. Mason Locke Weems (1759-1825) is the source of the story about George Washington and the cherry tree. When asked by his father if he had cut down the tree, the young Washington confessed. “I cannot tell a lie,” he said. Alas, the story itself is a lie.

The truth here is immaterial. What matters is that the tale’s once-wide acceptance shows how much we used to value honesty in our leaders. Now, though, they lie with abandon and, when caught, double down. You could call it the art of the deal.

I have just reviewed the herculean efforts of The Washington Post’s fact-checkers, limiting myself to the work they did following the GOP debates. Hands down, Donald Trump is the biggest liar of them all. (I’ll get to the Democrats another time.)

Trump said that “25 different [news] stories” proved he was always against the war in Iraq, stated that “almost every other country” does not grant birthright citizenship (even though about 30 do), said he hadn’t sought to open a casino in Florida, denied calling Marco Rubio “Mark Zuckerberg’s personal senator,” and concocted a tale that the family and “girlfriends” of the 9/11 hijackers went home to Saudi Arabia where “they wanted to watch their boyfriends on television.”

Like his fable that “thousands” of other Muslims in New Jersey cheered the collapse of the Twin Towers, none of that happened. Neither did a correction.

It would be unfair to the other liars to concentrate only on Trump. Carly Fiorina did very well indeed for a largely undercard candidate. Her most creative and passionate fib was that she had seen a video of a “fully formed fetus on the table, its heart beating, its legs kicking,” about to be carved up by Planned Parenthood for sale of its body parts. It’s entirely possible she was convinced she had seen something like that, but when confronted by the fact that no such tape exists, she insisted she had seen it. The woman does not have the truth in her.

Chris Christie also ranks high. Mr. Tell-It-Like-It-Is insisted on saying that he was “appointed” U.S. attorney for New Jersey on Sept. 10, 2001, a momentous one day before the terrorist attacks. Actually, his nomination came Dec. 7. When fact-checkers the world over pointed this out, Christie responded by saying it again.

My perusal of the fact-checkers’ work indicates that Jeb Bush and John Kasich did not do their share of lying. Marco Rubio and Ted Cruz had their innings and it was hard to tell if Ben Carson was lying or merely on meds. Still, no one approaches Trump. I think he would be proud.

Back in the 1950s, Sen. Joseph McCarthy played the press for chumps. He lied, made false accusation after false accusation, concocted figures — the number of purported communists in the State Department, for instance — and newspapers printed nearly every word of it. The press felt its hands were tied. It had to publish what an important senator said. It could not label a lie as a lie. That was a determination for the reader to make.

Trump has similarly played the media for chumps. For some cable networks, he is a profit center — and they have often covered him live, to the point of exhaustion. The proliferation of fact-checkers — missing in the McCarthy era — has not made any difference. Trump, like Fiorina in particular, never even concedes a mistake. He saw Muslims cheering in Jersey City on Sept. 11. She saw a fetus, alive and literarily kicking.

Politics is not beanbag, we are incessantly told. I get the point, even though I am not sure what beanbag is. And I know also that lying is very American. It is the basis for advertising — after all, one product is often little different than another.

Even as a kid, I never fell for that bit about George Washington and the cherry tree. But as an adult, I have come to value its larger message: Honesty is a virtue and lying is a vice. It is not news to me that politicians sometimes lie, but the frequency and blatancy of it in this election cycle are really astounding. This time, it’s not the media that are being played for chumps. It’s the American people.

Richard Cohen is a columnist for The Washington Post. His email address is: cohenr@washpost.com.