Sen. Bernie Sanders's (I-Vt.) campaign aides are questioning the polls and venting frustration with the news media, arguing that a biased political press is writing him off or blackballing him from coverage of the 2020 Democratic presidential primary.

Sanders is in second or third place in many national and early-state polls, but his campaign has struggled to overcome the emerging narrative that his moment has passed.

After electrifying the liberal base as the lone serious challenger to Hillary Clinton in 2016, Sanders has at times been overshadowed in his second presidential run by Sens. Elizabeth Warren (D-Mass.) and Kamala Harris (D-Calif.), who have generated buzz and excitement as they've risen in the polls.

Sanders campaign aides have taken notice, arguing that public opinion surveys don't capture their young, enthusiastic base of supporters or the new voters they say they're bringing into the fold.

And the campaign is turning its allegations of unfair media coverage into a rallying cry, telling supporters that the news media's inherent bias, obsession with horse-race politics about who is rising and falling, and the propensity to give outsize coverage to new candidates has led to a Sanders blackout that gives a false impression about the state of the race.

"Every time there is a story about how Bernie can't win, it fans the flame of our base and we get more donations and more volunteers," said one Sanders campaign aide who is not authorized to speak on the record.

"We'll never be the favorites in the media. I get it. But when was the last time one of these pundits visited a field office or talked to a state director? The bottom line is we have 2 million [donors] who have bought stock in what we're trying to do. That's powerful. If the media doesn't want to tell that story, that's fine. It just means we have to out-hustle these other campaigns."

Sanders's critics say it's up to the candidate to reinvent himself in a way that makes him stand out.

Some Democrats say he's been a one-note candidate, always pivoting off the political debate of the day to return to the same anti-corporate message that he's honed over decades.

"He's almost like a greatest hits act," said one Democratic operative.

Others say that Sanders has failed to broaden his appeal beyond a core bloc of progressive voters.

"The challenge here is getting news editors to see him as newsworthy when he's not moving in the race," said one Democratic strategist with close ties to the progressive movement. "The reality is he's having a hard time expanding. It's completely OK for the media to point this out. The media is reporting on real movement in a dynamic race. This is not 2016 where he was the only other option."

On Sunday's "Meet the Press," NBC anchor Chuck Todd confronted Sanders with criticism that his 2020 campaign sounds exactly like his 2016 campaign.

Sanders responded that he will change what he's saying, "when the poor get richer and the rich get poorer, when all of our people have health care as a right, when we are leading the world in the fight against climate change."

The Sanders campaign is taking its grievances with the media directly to supporters.

In a recent video uploaded to YouTube, top campaign aides unloaded on what they described as media bias against them.

Ari Rabin-Havt, the chief of staff for the Sanders campaign, said "there's an institutional bias in the media for something new" and the press is no longer interested in covering the proposals Sanders brought to the forefront in the 2016 campaign that have since become mainstream in the Democratic Party.

Rabin-Havt highlighted the "insidious" instances in which the media wrote up polls that showed Sanders firmly in second place but the headlines and leads of the stories focused instead on Harris and Warren rising into third or fourth place.

And he suggested that the top levels of the political press don't understand Sanders's appeal because they're disconnected from ordinary Americans.

"The elite media, the media that's at the top, the cable nets, the lead editors, the reporters, they tend to live in Washington, D.C., or New York," Rabin-Havt said. "They tend to be upper-middle class or wealthy. They work for companies worth billions of dollars. So on TV you have millionaires paid by billionaires to present information."

The polls have been a sore spot for the Sanders campaign, as recent public opinion surveys have shown Harris and Warren catching or surpassing Sanders in some national and early-voting state surveys, but not all.

A Saint Anselm College poll of New Hampshire released Monday found Sanders in fifth place, at 10 percent support.

"That poll has me 3.4 percent among young people," Sanders said Tuesday at a Washington Post event. "That poll is a bad poll."

Sanders's allies argue that in 2016, pollsters routinely underestimated his base of support and failed to account for young or new voters who supported him.

They say they have an unparalleled network of volunteers and point to the fact that they've raised more money than any other candidate in the first two quarters of the year from about 2 million individual small-dollar donors.

In Iowa, for instance, where Sanders outperformed expectations in 2016, his campaign has carefully built up a massive turnout operation aimed at turning nonvoters into highly motivated caucusgoers.

"I think the polling probably underestimates his support, because last caucus what happened is he exceeded the polls," Rep. Ro Khanna (D-Calif.), a co-chair of Sanders's campaign, said. "There were about 10,000, 12,000 people who showed up the day of the caucus who registered as Democrats to vote."

Khanna said that Sanders's support is strongest in Iowa, the first-in-the-nation caucus state, and California, which will vote on Super Tuesday. Both states will be critical in determining the Democratic nominee.

"I think his support in Iowa is very, very strong," Khanna said. "He's got one of the best ground teams. I was all over the state and he's got numerous volunteers showing up to help canvass and call this early."

But Monmouth University pollster Patrick Murray said he has come across a significant chunk of 2016 Sanders supporters who are giving the other candidates a serious look.

Murray agreed that pollsters don't know what the 2020 electorate will look like and that it's possible new voters will propel Sanders to victory. But he said surveys showing Harris and Warren on the rise and cutting into Sanders's support are an accurate reflection of the state of the race, at least at this early stage when support for all of the candidates is "soft."

"We don't know who will show up, the polls are not clear on what the electorate will look like," Murray said. "But the overall trend of where the different candidates are moving is real. There are Sanders voters from 2016 who are looking seriously at other candidates, and that's why his support isn't where it was last time. Some might not go back to him because of the plethora of candidates to choose from."