WASHINGTON — A series of online polls showing Donald Trump winning Monday night’s debate were rigged, according to a report on Tuesday.

While mainstream media and pundits quickly crowned Hillary Clinton the winner, Trump touted several online polls showing that he triumphed.

“Such a great honor. Final debate polls are in — and the MOVEMENT wins,” Trump tweeted.

Online polls aren’t given much credence because they aren’t scientifically representative samples of the electorate.

But The Daily Dot suggested online results from about 70 debate polls were particularly egregious because Trump supporters “artificially manipulated” the results “to create the false narrative” that he won.

Trump supporters using Reddit and 4chan message boards bombarded the online polls and spread the effort to Twitter to catapult the hashtag “#Trumpwon” to the No. 1 trending topic.

Established pollster Neil Newhouse says online surveys encourage a “stuffing the ballot box” mentality.

“Whenever news outlets ask readers their opinions online, and open it to everyone who visits their webpage, it’s not a valid poll, no matter how many people participate,” Newhouse, co-founder of Public Opinion Strategies, a political survey and polling firm, told The Post.

“That’s akin to a Major League Baseball team putting the All-Star ballot on their website. It’s not a random sampling of respondents.”

Newhouse was Mitt Romney’s pollster in 2012.

“At the same time, the polls that were supposedly ‘manipulated’ weren’t actually polls to begin with. They are nothing more than ‘click-bait’ to get people to respond. Ignore these polls. They are not measuring what they purport to and are really quite worthless.”

Trump stood by the online polling results.

“Mr. Trump won the debate and that is reflected in the online polls, which show a landslide victory,” Trump spokeswoman Hope Hicks told The Post.

News outlets admit their results are far from scientific.

“Online reader polls like this one are not statistically representative of likely voters, and are not predictive of how the debate outcome will affect the election,” Time.com wrote in an online disclaimer. The Time poll shows Trump won 56 percent to 44 percent with 1.8 million responses.

“They are a measure, however imprecise, of which candidates have the most energized online supporters, or most social media savvy fan base.”