Supporters greet Democratic presidential candidate Bernie Sanders at a rally in Carson, California, U.S., May 17, 2016. (Photo by Lucy Nicholson/Reuters)





A young female supporter wears a tattoo on her face as she attends a rally for U.S. Democratic presidential candidate Bernie Sanders in Vista, California, United States May 22, 2016. (Photo by Mike Blake/Reuters)





U.S. Democratic presidential candidate Bernie Sanders organizes a picture with the Rancho Buena Vista High School marching band after they played at a rally for Sanders at their High School in Vista, California, United States May 22, 2016. (Photo by Mike Blake/Reuters)





Supporters for U S. Democratic presidential candidate Bernie Sanders yell out during Sanders' speech at a campaign rally in Irvine, California U.S. May 22, 2016. (Photo by Alex Gallardo/Reuters)





Pinatas lie on the ground before U.S. Democratic presidential candidate Bernie Sanders speaks in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





A supporter waits for U.S. Democratic presidential candidate Bernie Sanders to speak in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





A supporter waits for U.S. Democratic presidential candidate Bernie Sanders to speak in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporter Koelen Andrews, 34, waits for U.S. Democratic presidential candidate Bernie Sanders to speak in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporter Mette Peluce, 11, waits for U.S. Democratic presidential candidate Bernie Sanders to speak in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





U.S. Democratic presidential candidate Bernie Sanders shakes hands with supporters after speaking in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





U.S. Democratic presidential candidate Bernie Sanders speaks in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporter Maria Antonio waits for U.S. Democratic presidential candidate Bernie Sanders to speak in East Los Angeles, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporters wait for U.S. Democratic presidential candidate Bernie Sanders to speak in Santa Monica, California, U.S., May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Ariella Reiss (L) poses while dressed as U.S. Democratic presidential candidate Bernie Sanders before a campaign rally in Santa Monica, California, U.S., May 23, 2016. (Photo by Lucy Nicholson/Reuters)





U.S. Democratic presidential candidate Bernie Sanders speaks in Santa Monica, California, U.S., May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporters wait for U.S. Democratic presidential candidate Bernie Sanders to speak in Santa Monica, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Devon Slack, 16, waits for U.S. Democratic presidential candidate Bernie Sanders to speak in Santa Monica, California, U.S., May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Supporters jump for a friend's photo as they wait for U.S. Democratic presidential candidate Bernie Sanders to speak in Santa Monica, California, U.S. May 23, 2016. (Photo by Lucy Nicholson/Reuters)





A supporter waits for U.S. Democratic presidential candidate Bernie Sanders to speak in Santa Monica, California, U.S., May 23, 2016. (Photo by Lucy Nicholson/Reuters)





Democratic presidential candidate Sen.Bernie Sanders (D-VT) speaks during a campaign rally on May 10, 2016 in Stockton, California. Sanders is campaigning in California ahead of the state's June 7th presidential primary. (Photo by Justin Sullivan/Getty Images)





Democratic presidential candidate Sen. Bernie Sanders and wife Jane O'Meara Sanders arrive to a campaign rally at California State University, Dominguez Hills on May 17, 2016 in Carson, California. Candidates are campaigning for the June 7 California presidential primary election. (Photo by David McNew/Getty Images)





Supporters of Democratic presidential candidate Bernie Sanders attend an election night rally in Carson, California, May 17, 2016. Sanders scored a decisive victory over Hillary Clinton in the Democratic primary in Oregon, boosting his argument for keeping his underdog campaign alive through the conclusion of the primary process. Several US networks called the Pacific northwest state for the liberal Sanders, who was leading the former secretary of state 53 percent to 47 percent. Earlier in the night, Clinton claimed victory in an extraordinarily tight race in the state of Kentucky. (Photo by Robyn Beck/AFP Photo)





Democratic presidential candidate Bernie Sanders addresses a primary night election rally in Carson, California, May 17, 2016. (Photo by Robyn Beck/AFP Photo)





Democratic presidential candidate Bernie Sanders shakes hands with a man holding a beer while taking a walk through San Francisco, California on May 18, 2016. (Photo by Josh Edelson/AFP Photo)





Democratic presidential candidate Bernie Sanders addresses supporters during a rally, May 21, 2016 in National City, California. (Photo by Sandy Huffaker/AFP Photo)





Bernie Sanders supporter Arely Ramos of Chula Vista takes a self with Mike Johnson of Linda Vista, wearing a paper mache Bernie Sanders head while they wait for the doors to the rally in Kimball Park to open Saturday, May 21, 2016 in National City, Calif. (Photo by Howard Lipin/The San Diego Union-Tribune via AP Photo)





Presidential candidate, Bernie Sanders speaks at a rally at Santa Monica High School on Monday May 23, 2016 in Santa Monica, CA. The primary in California is June 7th. (Photo by Matt McClain/The Washington Post)





UCLA student, Maral Milani, center, cheers for presidential candidate, Bernie Sanders as he speaks at a rally at Santa Monica High School on Monday May 23, 2016 in Santa Monica, CA. The primary in California is June 7th. (Photo by Matt McClain/The Washington Post)





Presidential candidate, Bernie Sanders speaks at a rally at Santa Monica High School on Monday May 23, 2016 in Santa Monica, CA. The primary in California is June 7th. (Photo by Matt McClain/The Washington Post)





A person dressed as presidential candidate, Bernie Sanders is seen at a rally at Santa Monica High School on Monday May 23, 2016 in Santa Monica, CA. The primary in California is June 7th. (Photo by Matt McClain/The Washington Post)





Presidential candidate, Bernie Sanders greets people after speaking at a rally at the Anaheim Convention Center on Tuesday May 24, 2016 in Anaheim, CA. The primary in California is June 7th. (Photo by Matt McClain/The Washington Post)