President Trump Donald John Trump2 women win Georgia Dem runoffs, extending streak for female candidates Giuliani on Trump-Cohen audio: 'I've dealt with much worse tapes than this' Roseanne to sit down with Hannity in first television interview since ABC canceled show MORE is concerned about the prospect of running against former Vice President Joe Biden Joseph (Joe) Robinette BidenClapper: 'Very petty' that Trump is considering revoking security clearances Juan Williams: Dems can beat Trump with the white working class Kerry: Trump attacks on Biden are 'unbecoming of a president' MORE in 2020, fearing that he is the Democrat most capable of reaching his base of white working-class voters, Axios reported Wednesday.

Advisers to the president tell Axios that Biden is seen as the potential Democratic challenger to Trump most likely to put up a fierce fight in states that Trump won in 2016, like Pennsylvania, Michigan and Wisconsin.

Trump also considers Biden a potential threat because of what he sees as an otherwise weak set of rumored Democratic challengers, like Sens. Bernie Sanders Bernard (Bernie) SandersOcasio-Cortez tiptoes into Washington Overnight Health Care: House votes to repeal medical device tax | Fierce ObamaCare critic joins administration | GOP senators target DC individual mandate On Nicaragua, the silence of the left is deafening MORE (I-Vt.) and Elizabeth Warren Elizabeth Ann WarrenBooker: Those who don't oppose Kavanaugh are 'complicit in the evil' Tenn. Republicans to go on offense against Dem Overnight Defense: Questions mount over Trump's Iran tweet | House, Senate unveil compromise defense bill | Bill includes Russia sanctions waivers, limits on Turkey's access to F-35 | Endangered species measures dropped MORE (D-Mass.), Axios reported.

To be sure, Biden has not said yet whether he intends to challenge Trump in 2020. But he has repeatedly been floated as a potential contender and has left the door open to a presidential bid.

Biden, a former senator from Delaware, has long touted his hometown of Scranton, Pa. as a symbol of his working-class upbringing.

That could ultimately make areas of Pennsylvania outside of Philadelphia and Pittsburg more competitive. Trump campaigned fervently across the state in 2016 and relies heavily on support from more suburban and rural areas for support, Axios reported.

The news outlet reports that Biden will wade more heavily into electoral politics in the fall by appearing with candidates across the country on a weekly basis and issuing a series of endorsements.