Advisers to President Trump say Joe Biden is the Democrat he most fears running against, and that Pennsylvania is the state he worries most about flipping against him.

Trump’s calculation is based partly on how weak he sees other Democratic possibilities, including Bernie Sanders or Elizabeth Warren, and partly on who’s capable of appealing to his base of working class whites…

A Democratic source close to Biden said he’d be strong with “Obama-Trump voters” in states like Pennsylvania, Michigan and Wisconsin where “the blue wall became the red threat” — Obama won them twice, then they flipped narrowly to Trump.

These are white, working-class voters who aren’t college graduates (or have some college) and are anti-Washington. They voted for the anti-establishment candidate (Obama) in 2008 and again in 2016.