A guide to the 37 Democrats who may or may not be running for president

    U.S. Sen. Cory Booker, D-NJ, leaves ABC studios in New York after an appearance on The View, Friday, Feb. 1, 2019. Booker on Friday declared his bid for the presidency in 2020 with a sweeping call to unite a deeply polarized nation around a "common purpose." (AP Photo/Mark Lennihan)

    With Sen. Cory Booker, D-N.J., entering the 2020 Democratic presidential race Friday and just over a year between now and the Iowa caucus, t