Now Playing: Pentagon to send 1,000 troops to Middle East

Now Playing: President Trump claims to have a plan for health care ahead of his campaign launch

Now Playing: Health care on Trump's mind as he kicks of 2020 campaign

Now Playing: Soaring prices force some to travel for insulin

Now Playing: Trump says 'the polls don't exist' in tell-all interview

Now Playing: Alexandria Ocasio-Cortez says it's 'too early to endorse' presidential candidate

Now Playing: Trump fires pollster after numbers leak

Now Playing: Reaction grows to Trump comments on Mueller, finances

Now Playing: Trump says historic redesign of Air Force One holds 'secrets': Part 6

Now Playing: Trump defends decision not to sit for an in-person interview with Mueller: Part 5

Now Playing: Trump says Kim Jong Un 'promised me he wouldn't be testing' nuclear weapons: Part 4

Now Playing: Trump says if foreign government offered opponent dirt: 'I'd want to hear it': Part 3

Now Playing: Trump on Mueller, immigration and putting his personal touch on Oval Office: Part 2

Now Playing: Trump on polls showing Biden ahead: 'I don't believe those polls': Part 1

Now Playing: Trump responds to answering questions about obstruction

Now Playing: Trump on his relationship with North Korean leader Kim Jong Un today

Now Playing: Trump accusing New York Times of a 'virtual act of treason'

Now Playing: Trump campaign has cut ties with some of its pollsters after data was leaked

Now Playing: A rare look inside Air Force One

Now Playing: 'Prime opportunity' for Elizabeth Warren 'to shine': Rick Klein on Dem debate lineup