President Trump has been quick to use Twitter as a weapon against his critics in the media. He’s even attacked some anchors on his favorite outlet, Fox News.

But this past summer one thing in particular seemed to get under the president’s skin: Fox News’ polls, which recently showed him trailing four potential Democratic opponents in the 2020 race for the White House and having a 56% disapproval rating of his job performance.

“My worst polls have always been from Fox,” Trump told reporters in August. “There’s something going on at Fox, and I tell you I’m not happy with it.”

Trump’s comments were surprising to some observers who see Fox News as the president’s main media cheerleader. But the conservative news network’s political unit has a long-running reputation of being a nonpartisan source of research on voting and public opinion — even if its findings irritate the Fox News fan watching in the White House.

Fox News digital politics editor Chris Stirewalt, who serves as the network’s main on-air analyst of polls and voting trends, does not take Trump’s shots at his operation personally.

“When Trump does things like this, people say ‘Can you believe it?’ ” Stirewalt, 43, said at Fox News headquarters in midtown Manhattan. “And I say, ‘Yes, of course I can believe it because every political figure in every cycle has done it.’ Complaining and trying to game the refs about polls and coverage is not a new thing.”

Veteran political operatives say the Fox News polls have always been insulated from any kind of partisan slant.

“They are just honest numbers,” said veteran Democratic pollster Joel Benenson, chief executive of Benenson Strategy Group in New York. “Trump doesn’t like them because they are honest numbers and they are horrible for him.”

Stirewalt and the political unit that oversees the polling are key elements in the network’s Washington bureau, where its anchors Bret Baier and Chris Wallace and its correspondents steer clear of the kind of fiery conservative commentary that contributes to Fox News’ reputation as a bulwark for the Trump White House.

Trump has been known to rely on Fox News opinion hosts such as Sean Hannity and Tucker Carlson for solace and policy advice. But the president gets no help when he is unhappy over Fox News polls on his performance or how he fares against his potential Democratic opponents in the 2020 race for the White House.

If Trump calls to complain about the numbers to Fox News executives or even Rupert Murdoch, chairman of parent company Fox, it never filters down to Stirewalt or his colleagues, he said.

“I don’t hear boo,” said Stirewalt, a veteran political journalist from West Virginia who joined Fox News in 2010. “I’ve never been asked. I have never been leaned on. I have never had a gust blown in my direction that ‘it might be a little bit better if …’ ”

The even-handedness of the operation got the backing of Nate Silver, the political research guru who oversees the ABC News-owned web site FiveThirtyEight. He gave the Fox News poll an “A” rating — based on accuracy and methodology — in a report card of pollsters he issued in May 2018.

The Fox News poll of support for the 2020 presidential primary contenders is trusted enough by the Democratic National Committee to be one of the surveys used to determine who qualifies to take the stage in its debates.

The reliability of the Fox News polling data has not been enough to reverse the DNC’s decision to shut the channel out of the primary debates. DNC Chairman Tom Perez has said he respects the Washington correspondents at Fox News but believes the network’s overall slant favors the Republicans.

The stance has deprived Fox of the DNC-sanctioned events that have delivered large audiences for NBC, ABC and CNN.

Stirewalt said he continues to lobby the DNC for a debate for Fox News. A self-proclaimed numbers nerd who as a child badgered his parents for a copy of the Statistical Abstract of the United States, he stands by the independence of the channel’s Washington bureau and polling experts.

These experts include Arnon Mishkin, a Fox News contributor and director of the network’s “decision desk” — a group of political scientists and statistical analysts who decide when to call races during the network’s election coverage. Early in his career, Mishkin worked on campaigns with legendary New York political consultant David Garth, who handled moderate candidates from both parties.

Dana Blanton, vice president of public opinion research at Fox News, has overseen polling at the network since it launched in 1996, not long after she earned a master’s in business administration from George Washington University.

According to former colleagues, she is known for being methodical and inscrutable, offering no hint of her own political views.

Since 2011, Blanton has used a bipartisan team to gather data for Fox News — Beacon Research President Chris Anderson, a Democrat; and Daron Shaw, a Republican, of Shaw & Co. Research. The two-party setup is similar to how the NBC News/Wall Street Journal poll is conducted. Both Anderson and Shaw work on the decision desk for Fox on election nights.

Trump has asserted that even Fox News polls were wrong in predicting that Hillary Clinton was leading going into election day in 2016. But Fox was in line with other news organizations in predicting Clinton would win the popular vote.

“We spend a lot of time reminding people that the polls were right,” Blanton said. “Almost all of the national polls had Clinton leading by 2 to 4 points, and she won by just over 2 in the national popular vote.”

Still, Stirewalt, Mishkin and Blanton have to navigate a fiercely polarized environment where the numbers they deliver can elicit angry responses from all sides. Blanton said she avoids reading the vituperative reader comments when she writes a data-based analysis for FoxNews.com.

The political unit has had to stand its ground on election nights as well. During coverage of the 2018 campaign, the Fox News decision desk was the first to project that the Democrats would win back a majority of the House of Representatives.

The network’s anchors announced the call at 9:30 p.m. Eastern time, a full hour before its competitors.

Democratic activists distrustful of Fox News used social media to denounce the call, suggesting it was a “false flag” meant to discourage their party’s voters from casting ballots on the West Coast, where polls were still open.

True believers on the Republican side have also expressed skepticism when Fox News calls races that don’t go their way. The dynamic played out dramatically in 2012 during Fox News coverage of Barack Obama’s victory over Republican opponent Mitt Romney for a second term in the White House.

That night, Republican strategist Karl Rove, a Fox News commentator, disputed his own network’s decision desk call that Obama had won Ohio’s electoral votes and another term in the White House. A commentator questioning the announced results of the network he worked for was unprecedented.

Rove’s remarks prompted then-Fox News anchor Megyn Kelly to leave the set and walk through the corridors of the network’s headquarters and into the secluded room where the decision desk was tabulating and analyzing the vote (Stirewalt refers to the room as the “nerdquarium”).

Although the visit is often remembered as a format-breaking stunt, producers had rehearsed the walk to the decision desk by Kelly and co-anchor Baier to get the camera angles and lighting correct. They had also told viewers in advance they might talk to the analysts if a question arose about the results.

But Stirewalt and Mishkin did not know Rove would be taking issue with their work on live TV.

When Kelly showed up at the decision desk, Stirewalt and Mishkin told her there were simply not enough uncounted votes in traditionally Republican districts in Ohio to offset the strong Democratic numbers they were seeing in the state’s urban centers.

“What made it fun for us is we had it,” said Stirewalt. “It was a dead certainty.”

“What I wanted to say that night was, ‘Tell Karl if he doesn’t like that, wait until we call Florida,’ ” Mishkin added. Obama won that state as well.

The 2012 moment is referenced in Showtime’s recent limited series “The Loudest Voice,” which dramatizes the career of Roger Ailes, the late Fox News chairman. Ailes, played by Russell Crowe, is seen agonizing over Obama’s victory and telling an executive to have Rove delay the decision desk’s call of the election.

But no such directive was given, as Ailes had seen exit polling data earlier that pointed to an Obama win, Mishkin said.

“I briefed Roger that evening, and I can tell you, none of that is true,” said Mishkin. “That is all fiction.”

Mishkin, who has worked at the Fox News decision desk on election nights since 1998, said executives have never dictated when a call should be made even if the results might cause conservatives in the audience to tune out.

Fox News is hoping to sharpen its polling acumen even further in the 2020 presidential campaign.

In 2017, Fox News and the Associated Press decided to break away from the consortium of news organizations that pool their resources to do exit polling during elections. The group also includes ABC, CBS, NBC and CNN.

Fox News and the AP sought a new polling methodology after seeing that in-person questioning done at polling locations in key states proved less reliable in predicting the outcomes of the presidential elections of 2000, 2004 and 2016.

In all three cases, exit polls showed losing Democratic nominees Al Gore, John Kerry and Hillary Clinton being ahead.

The two outlets teamed with the National Opinion Research Center at the University of Chicago to develop a new election survey that increases the number of people questioned and puts a greater emphasis on early voting.

Fox News tested the new system in several special elections, including the tight 2017 contest for Alabama’s U.S. Senate seat. It accurately called the narrow victory for Democratic nominee Doug Jones over Republican Roy Moore before its competitors CNN and MSNBC.

The same system enabled the decision desk to make the early declaration that the Democrats had won the House last year.

The so-called Fox News Voter Analysis combined extensive online questioning of 117,000 people with historical precinct-by-precinct voting data. The researchers even interviewed people who stayed home on election day to learn why they didn’t vote.

During the Democratic primaries and caucuses in 2020, the Fox News Voter Analysis will poll 1,500 to 2,500 voters in each state to try to deliver the most accurate read on who is ahead in the race for the nomination.

“In the primaries, we’re developing a set of tools to be sure we can assess last-minute swings,” Mishkin said. “It’s not just a snapshot of what happens on primary days; it will also be a snapshot of what happens before the primary. You can tell why candidate X emerged from nowhere.”

While the political unit’s work evolves, one ritual will stay the same. Before every election night he works, Mishkin, 64, relaxes by taking out his cello and playing the first two Bach suites for cello.

“It was something I adopted in midlife,” said Mishkin, who first took lessons in grade school. “My daughter tells me, ‘Everyone’s father who has a midlife crisis buys a motorcycle. You get a cello.’ ”