The Drudge Report posted a 45 percent decline in web traffic in September as the site alienated its core readers by turning against President Trump ahead of the 2020 presidential election.

The data — derived from comScore, which tracks the industry — were released in a report by TheRighting, a website that analyzes traffic to right-leaning websites. TheRighting told The Post that the Drudge Report had 1,291,000 unique visitors in September, according to data supplied by comScore, down from 2,340,000 in the same month a year ago.

September’s eye-popping decline marks the ninth month in a row that the political news aggregation website run by reclusive founder Matt Drudge has seen traffic fall, TheRighting said.

The plunge comes at a time when demand for political news has been soaring on both sides of the aisle leading up to a highly charged presidential election. And experts say it’s directly tied to the Drudge Report’s sudden and unexpected switch earlier this year from a conservative-leaning news outlet to one that’s decidedly anti-Trump.

“It’s catastrophic what has happened to his web traffic,” said Matt Lysiak, author of “The Drudge Revolution.” “He’s on a fast track to irrelevance.”

Lysiak says some of the Drudge Report’s suffering can be traced to competition from social media services like Twitter. “But what accelerated his decline is when he shifted to the left and turned on Trump and lost many of his core readers. By any criteria, this shift was a complete disaster for him,” Lysiak said.

“Liberals are never going to love Drudge, even if he’s not linking to stories about Hunter Biden and Joe Biden,” Lysiak said of the website that made its name in the 1990s by being the first outlet to report on the brewing Monica Lewinsky scandal. “They’ll always remember what happened with Bill Clinton.”

Drudge had been an ardent promoter of Donald Trump in the run-up to the 2016 election and was reportedly invited to the White House in 2017. But the site and its founder have drawn criticism from readers, including the president, for linking to largely negative stories about the president in recent months.

Stories topping the Drudge Report on Friday included a link to a Washington Post article about Trump’s public musings over a potential loss to Joe Biden and a Pennlive.com story about growing regional delays in the US Postal Service’s delivery times.

“Congratulations Dan. You, Breitbart and others have decimated the business at Drudge,” the president tweeted earlier this month. “It’s gone the way of the @NBA, ratings down 70%. People want the TRUTH! Drudge Report sold out, suffered a massive ‘nervous breakdown’. Happening @FoxNews also???”

The “Dan” whom Trump congratulated appears to be Dan Bongino, founder of fast-growing Bongino.com, which saw its unique visitor traffic surge 780 percent in September, according to TheRighting.

Growing appetites for political news, meanwhile, have helped traffic to Fox News’ website grow 9 percent in September compared to a year ago, with 104.1 million unique visitors, The Righting said. That lags behind CNN, which pulled 144.5 million unique visitors, up 11 percent, but beats the New York Times brands’ 95.1 million unique visitors in September, up 3 percent compared to the same month a year ago, and the Washington Post with 91.6 million unique visitors, also up 3 percent from a year ago, TheRighting said.

Other right-leaning news sites that have benefited this election cycle are the Washington Examiner, which pulled 15.9 million unique visitors, up 11 percent, and The Blaze, which attracted 12.3 million unique visitors, up 106 percent, according to TheRighting.

The fastest-growing sites in September were Bongino.com, up 780 percent to 2.6 million unique visitors, according to TheRighting; The Gateway Pundit, up 456 percent to 5.7 million, and CNS News, up 417 percent to 3.9 million unique visitors.

“Strong audience growth for most conservative websites continues to be driven by a heated news environment that shows no signs of cooling off,” said Howard Polskin, president and chief curator at TheRighting, whose tagline is “Alerting liberal audiences to today’s headlines from the right.”

“Notable stories in September 2020 included the escalation of the pandemic, the dramatic revelations in Bob Woodward’s latest book on President Trump, the fireworks that characterized the first Trump-Biden debate, the death of Ruth Bader Ginsburg, the contentious nomination of Amy Coney Barrett to the Supreme Court and the explosive story in the New York Times about Trump’s tax returns,” Polskin said. “These stories played like a reality show and kept audiences thoroughly engaged throughout the month as they kept turning to news media to learn the latest unfolding developments.”

Down last month was right-wing conspiracy site InfoWars, founded by Alex Jones, which saw traffic fall 1 percent for the fifth month in a row, The Righting said. The Daily Caller also saw traffic drop 9 percent for the month as it recorded its second monthly decline in a row.