Now Playing: Trump says release of Mueller report while he's abroad is up to attorney general

Now Playing: North Carolina 9th District election fraud hearing

Now Playing: Tulsi Gabbard on why she's running for president

Now Playing: Who is Jeff Rosen, the new pick for deputy attorney general

Now Playing: Bernie Sanders raises six million dollars in one day

Now Playing: Pres. Trump denies interference in Michael Cohen investigation

Now Playing: Covington Catholic student's parents sue Washington Post

Now Playing: Trump denies he asked acting AG to replace prosecutor

Now Playing: Russia investigation timeline

Now Playing: Bernie Sanders raises $4M in 1st day of campaign

Now Playing: Bernie Sanders joins the 2020 presidential race

Now Playing: New report on alleged attempt by Trump to influence investigators

Now Playing: Trump's national emergency faces legal pushback

Now Playing: Minnesota attorney general talks about suing to block Trump from building border wall

Now Playing: Keith Ellison on Bernie Sanders' 2020 presidential bid

Now Playing: Biden: 'It's time to restore America's soul'

Now Playing: Michael Cohen's lawyer says Trump uses mafia-like tactics against his client

Now Playing: Andrew McCabe on his criticisms of former Attorney General Jeff Sessions

Now Playing: Andrew McCabe says he was 'absolutely not' a leaker to The New York Times

Now Playing: Andrew McCabe on President Trump's relationship with Russia