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"Probably about half the time throughout history, the candidate leading the polls now goes on to win his or her primary," Silver told Powerhouse Politics podcast hosts, ABC News' Chief White House Correspondent Jonathan Karl and Political Director Rick Klein.
Karl questioned the weight polls hold this early in the race, and Silver noted that Biden's numbers will probably fade in a few weeks after this "post-bounce period."
But Silver also pointed out that, "given that primaries typically consist of -- maybe not 20 candidates like we have now -- but usually consist of 10 or 12 candidates, is somewhat impressive, actually."
Four national polls released Tuesday all placed Biden at the front of the pack, and showed significant increases in support for him, Silver said Tuesday on FiveThirtyEight.
On average, Biden hovers around 36 or 37 percent, Silver said on Powerhouse Politics. And the former vice president pulled ahead in FiveThirtyEight's endorsement tracker just one day after announcing his run. But as of now, there's not an obvious number two in the race, Silver said.
While Biden is up, Sen. Bernie Sanders, Sen. Kamala Harris and former Congressman Beto O'Rourke are down in the polls. Sanders' decline to around 16 or 17 percent, may be due to Sen. Elizabeth Warren's improvement, Silver said. And South Bend, Indiana Mayor Pete Buttigieg is doing fine, "given his low name recognition," Silver said.
But despite the strong numbers backing Biden so far, Silver said he thinks the former vice president is actually being slightly overlooked by the media.
Biden's "supporters are not necessarily like the Twitter-following, podcast-listening demographic," Silver said. "It's more working class voters, older voters, a lot of African-Americans. So I do think he's underrated at the same time."
Two groups Silver said Biden resonates with: Voters over 50 and black Democrats.
"And that's a coalition that historically is very powerful in Democratic politics," Silver said.
In a CNN poll published Tuesday, Biden led the field with 50 percent of non-white Democrats/Democratic-leaning Independents and 50 percent of Democrats/Democratic-leaning Independents, 65-years-old and over, saying that they would be likely to support him for the nomination.
But it may not stay that way for long. Silver said he's spoken with Biden's campaign, who expect opponents like Harris or Sen. Cory Booker -- who are both black -- to "make a serious play" for the African-American vote.
And there may be more vulnerabilities lurking on the sidelines that could derail Biden's chances at returning to the White House, Silver said.
"I still really wonder how comfortable voters will be nominating someone who is now 76, or in Bernie's case, 77 years old," Silver said. "A lot of voters, if you poll them in the abstract and say, 'Do you feel comfortable with someone 75 or older being president?' They say, 'No I do not.'"
While Biden has positioned himself in opposition to President Donald Trump -- citing the president's comments in response to white supremacists in Charlottesville, Virginia and saying "we're in the battle for the soul of this nation" in an announcement video -- Silver thinks Democratic voters will seek a more diverse candidate to represent them.
"It doesn't make sense to me that you have these two or three or four white men who are leading the field and that you're not going to have Kamala Harris or Warren or Klobuchar or Cory Booker -- or someone who's not a white man -- catch up and be at least a big player in the race later on," Silver said.
Biden has had to address concerns about his past statements and policy positions, including his votes on criminal justice issues and treatment of Anita Hill.
In an interview with ABC's "Good Morning America" co-anchor Robin Roberts Monday, Biden said he takes responsibility for Hill's treatment in 1991 when she testified before the Senate Judiciary committee during Supreme Court Justice Clarence Thomas's confirmation hearing.
"I believed her from the very beginning, but I was chairman. She did not get a fair hearing. She did not get treated well. That's my responsibility," Biden said.
Biden has also defended his claim that he has, "one of the most progressive records of anyone running," despite the records of his more left-leaning rivals, like Sanders or Warren.
While Silver said he's "not sure that claim would withstand a fact check," he said Biden's long record in the public eye and ties to former President Barack Obama give him an edge on some of his lesser-known opponents.
Biden's claim "might withstand the scrutiny, ironically, of Democratic voters, because he was Obama's vice president for eight years," Silver said. "A lot of questions that you would have about some other old ex-senator who decided to run for office are not going to be asked by Democrats because he was the V.P., because he is closely tied to Obama and because Obama is still very popular among Democratic voters."
Silver noted that many of the ideas Biden has put forth so far are simple themes, such as restoring America. Meanwhile, candidates like Warren have churned out detailed policy proposals.
"It's very basic messaging but he has the advantage that because he is so well known he doesn't have to weave in all the biography," Silver said. "He doesn't have to explain why he should be the one you should pick for president, so much as 'here's what I stand for,' and cuts very straight to the actual conclusion."
While it remains to be seen who ultimately cinches the Democratic presidential nomination, Silver said Biden's chances are looking good.
"My main thesis right now is Biden's a front-runner. Doesn't mean he's the favorite to win relative to everyone else. It just means that he's more likely than anyone else one-on-one to win," Silver said.
Every Wednesday, ABC Radio and iTunes bring you the Powerhouse Politics Podcast which includes headliner interviews and in-depth looks at the people and events shaping U.S. politics. Hosted by ABC News' Chief White House Correspondent Jonathan Karl and ABC News Political Director Rick Klein.