There are a lot of Democrats who have hinted at running for president in 2020, but none of the many names send a shiver down President Trump's spine quite like "former Vice President Joe Biden."

Trump's advisers say he would be most concerned about his re-election if Biden was his Democratic competitor, Axios reported Wednesday. While he sees other potential candidates as weak, he thinks Biden could capitalize on Trump's own style to sway voters to go blue.

The president's previous claim that running against Biden would be a "dream" may have been a bluff, sources said, since he's privately worried that Biden could appeal to the blue-collar white voters that make up Trump's base. Biden "conveys authenticity," isn't afraid of a good verbal sparring match, and wouldn't hold back in getting under Trump's skin, advisers say. Additionally, the former VP is true to his Rust Belt roots, and could drum up support in working-class areas where Trump would desperately need wide margins to win again.

Lastly, Trump is reportedly most concerned about winning back Pennsylvania in 2020, especially if Biden, a Scranton native, took the lead as his opponent. The battleground state is sure to be hotly contested, and Democrats will be vying to flip it back in their favor. Biden has waded into talks of a presidential campaign, but has family matters that have kept him from jumping in entirely. On the other hand, he would reportedly view it as his last shot at politics, leaving him with "nothing to lose." Read more at Axios. Summer Meza