Eric Swalwell joins the 2020 Democratic nominee pool

Rep. Eric Swalwell (D-CA), accompanied by Rep. Joe Crowley (D-NY) and Rep. Ruben Kihuen (D-NV), speaks about revelations about President Donald Trump's involvement with Russia on Capitol Hill in Washington, D.C., U.S. May 17, 2017. Credit: REUTERS/Aaron P. Bernstein.

California Congressman Eric Swalwell has become the 18th Democratic candidate running for president in 2020. The field is already crowded. Former vice president Joe Biden is not officially in the running, but he leads in the polls, followed by Bernie Sanders.