Trump responds to Mueller request Video

Now Playing: The Briefing Room: Giuliani talks Mueller probe, congressman indicted for insider trading

Now Playing: Rep. Collins pleads not guilty

Now Playing: Trump responds to Mueller request

Now Playing: Manafort attorney alleges Rick Gates had multiple affairs

Now Playing: Less than 1 percent separates Ohio special election candidates

Now Playing: Balderson claims victory in Ohio, but O’Connor isn’t conceding yet

Now Playing: Explosive testimony in former Trump campaign chair’s financial crimes trial

Now Playing: Who is Rashida Tlaib?

Now Playing: Rick Gates returns to court to testify against his former boss Paul Manafort

Now Playing: Rep. Chris Collins arrested on insider trading charges

Now Playing: Behind the scenes of the Paul Manafort trial

Now Playing: Ohio special election results still unknown

Now Playing: High-stakes Ohio special election too close to call

Now Playing: Gates admits using embezzled money to fund affair

Now Playing: GOP’s Balderson inches ahead of O’Connor, Dems still not conceding

Now Playing: Ohio special election still neck and neck

Now Playing: AP projects Whitmer to win Democratic primary in Michigan

Now Playing: O’Connor holds early lead, hoping to give GOP huge upset

Now Playing: The Battle for the Buckeye State