Now Playing: Full Interview: Justice Stephen Breyer

Now Playing: LZ Granderson: Black Lives Matter 'Got White People to Pay Attention'

Now Playing: Veteran Moves Off the Streets to Apartment, In Time for Christmas

Now Playing: 'This Week' Powerhouse Puzzler

Now Playing: Why Matthew Dowd Thinks Biden May Regret Not Jumping in 2016 Race

Now Playing: Kristol on Donald Trump: 'I Think He Will Lose Iowa'

Now Playing: Kasich Dismisses Trump: 'He Complains About Everything'

Now Playing: 'This Week' Holiday Greetings 2015

Now Playing: Justice Stephen Breyer on Donald Trump, Civil Liberties and Retirement

Now Playing: Homeless Vet Gets an Apartment, Just in Time for Christmas

Now Playing: This Week in History: December 20-26

Now Playing: Trump Says He'll 'Get Along Fine' With Putin

Now Playing: Bernie Sanders: Donald Trump is a 'Pathological Liar'

Now Playing: Chris Christie: Hillary Clinton Is 'Mrs. Happy Talk' on ISIS

Now Playing: Clinton Campaign Doubles Down After Experts Question Claim About ISIS Videos Using Trump

Now Playing: Donald Trump Alleges Hillary Clinton Made up ISIS Video Claim

Now Playing: Dowd: 'Everybody Was After' Trump in Democratic Debate

Now Playing: Donald Trump Under Fire in Democratic Debate

Now Playing: Sun, Dec 20, 2015