Glenn Kessler’s final WaPo column as their fact checker:

In reviewing many of the some 3,000 fact checks I have written or edited, there is a clear dividing line: June 2015, the month Donald Trump rode down the Trump Tower escalator and announced he was running for president….

In ending its work with fact-checkers, Meta chief executive Mark Zuckerberg falsely claimed that fact-checkers censored free speech by being “too politically biased,” echoing Trump administration arguments. The Washington Post did not participate in the Meta program, but any Facebook user had the option to opt out of having posts fact-checked. Many fact-checkers would liken their work to nutritional labels on snack foods — providing more information about online content. People are free to ignore the warnings, just as people can ignore nutritional labels….

In 2016, Trump’s opponents still cared about the facts. Florida Gov. Jeb Bush’s (R) campaign had a wall where they posted positive fact checks. Ohio Gov. John Kasich (R) dropped a talking point simply in response to my question for a possible fact check. Hillary Clinton’s staff worked hard to find policy experts to vouch for her statistics. (Her comments on her private email server were less defensible).

But Trump didn’t care. He kept rising in the polls and eventually won the presidency. Other politicians took notice and followed his lead.

Besides Trump, something else changed the nature of truth in the mid-2010s: the rise of social media. The Fact Checker was launched in 2007, one year after the creation of Twitter and when Facebook had only 50 million users. By 2012, Facebook had 1 billion followers; it reached nearly 1.6 billion in 2015. Trump adroitly used Twitter — where he had 2.76 million followers at the start of 2015 — and other social media to spread his message. Trump’s call to ban Muslims from entering the United States was the most talked about moment on Facebook among the 2016 candidates in all of 2015, according to Facebook data.

Social media helped fuel the rise of Trump — and made it easier for false claims to circulate. Russian operatives in 2016 used fake accounts on social media to spread disinformation and create divisive content — tactics that led companies such as Meta to begin to use fact-checkers to identify misleading content. But the political forces which benefited from false information — such as Trump and his allies — led a backlash against such efforts, saying it was a form of censorship. Now tech companies are scaling back their efforts to combat misinformation….

During Trump’s first term, The Fact Checker team documented that he made more than 30,000 false or misleading claims. Week after week, I would write fact checks unpacking his latest misstatements, and Trump generally earned Four Pinocchios — the rating for a whopper. But I sense that the country has gotten so used to Trump exaggerating the truth that it no longer seems surprising. I chose not to repeat the exercise in his second term…