Secret Service agents remove a man from the crowd during a campaign rally for Democratic presidential candidate, Sen. Bernie Sanders, I-Vt., at Frank Ogawa Plaza in Oakland, Calif., on Monday, May 30, 2016. A group of animal rights activists briefly interrupted the Sanders rally in Northern California when they jumped barricades and tried to rush the podium. Sanders' security stopped the protesters before they could reach Sanders, who was addressing supporters at the rally and continued his speech within minutes of the disruption. (Photo by Anda Chu/Oakland Tribune via AP Photo)





Chris Zachos, of San Francisco, wears a homemade Democratic presidential candidate, Sen. Bernie Sanders, I-Vt., suit while attending a Sanders campaign rally at Frank Ogawa Plaza at Oakland's City Hall, in Calif., on Monday, May 30, 2016. (Photo by Anda Chu/Oakland Tribune via AP Photo)





U.S. Democratic presidential candidate Bernie Sanders greets supporters after a campaign rally in Santa Maria, California, U.S. May 28, 2016. (Photo by Lucy Nicholson/Reuters)





Supporters wait for U.S. Democratic presidential candidate Bernie Sanders to speak at a campaign rally in Santa Barbara, California, U.S. May 28, 2016. (Photo by Lucy Nicholson/Reuters)





Libertarian Party candidate Vermin Supreme (L), wears his signature boot, with supporters at the National Convention held at the Rosen Center in Orlando, Florida, May 29, 2016. (Photo by Kevin Kolczynski/Reuters)





People watch Republican U.S. presidential candidate Donald Trump address the Rolling Thunder motorcycle rally, which highlights POW-MIA issues, on Memorial Day weekend in Washington, U.S. May 29, 2016. (Photo by Jonathan Ernst/Reuters)





Nyla Joseph, 9, a daughter of a U.S. military veteran demonstrates with veterans outside Republican presidential candidate Donald Trump's news conference outside Trump Tower in New York, U.S., May 31, 2016. (Photo by Shannon Stapleton/Reuters)





A man demonstrates outside Republican presidential candidate Donald Trump's news conference at Trump Tower in New York, U.S., May 31, 2016. (Photo by Shannon Stapleton/Reuters)





An attendee reacts as Democratic U.S. presidential candidate Bernie Sanders prepares to enter Kaiser Permanente Arena during a campaign rally in Santa Cruz, California May 31, 2016. (Photo by Stephen Lam/Reuters)





Bernie Sanders supporter Drew Rainer dances prior to the U S. Democratic presidential candidate's campaign rally at Colton Hall in Monterey, California, U.S., May 31, 2016. (Photo by Michael Fiala/Reuters)





A Bernie Sanders supporter texts before the U S. Democratic presidential candidate's campaign rally at Colton Hall in Monterey, California, U.S., May 31, 2016. (Photo by Michael Fiala/Reuters)





Zaina (L) and Zahra Diallo play before U S. Democratic presidential candidate Bernie Sanders' campaign rally at Colton Hall in Monterey, California, U.S., May 31, 2016. (Photo by Michael Fiala/Reuters)





Bernie Sanders artwork by Amanda Burkman is displayed before the U S. Democratic presidential candidate's campaign rally at Colton Hall in Monterey, California, U.S., May 31, 2016. (Photo by Michael Fiala/Reuters)





U S. Democratic presidential candidate Bernie Sanders speaks during a campaign rally at Colton Hall in Monterey, California, U.S., May 31, 2016. (Photo by Michael Fiala/Reuters)





Democratic U.S. presidential candidate Hillary Clinton poses with supporters after a campaign event at Rutgers University's Newark campus in Newark, New Jersey, U.S., June 1, 2016. (Photo by Adrees Latif/Reuters)





Supporters cheer for U.S. Republican presidential candidate Donald Trump at a campaign rally in Sacramento, California, U.S. June 1, 2016. (Photo by Lucy Nicholson/Reuters)





Police form a line to contain protesters outside a campaign rally for Republican presidential candidate Donald Trump on Thursday, June 2, 2016, in San Jose, Calif. A group of protesters attacked Trump supporters who were leaving the presidential candidate's rally in San Jose on Thursday night. A dozen or more people were punched, at least one person was pelted with an egg and Trump hats grabbed from supporters were set on fire on the ground. (Photo by Noah Berger/AP Photo)





Supporters wait for U.S. Republican presidential candidate Donald Trump to speak at a campaign rally in Sacramento, California, U.S. June 1, 2016. (Photo by Lucy Nicholson/Reuters)





U.S. Democratic presidential candidate Hillary Clinton waves to someone in the crowd after delivering a speech on national security in San Diego, California, United States June 2, 2016. (Photo by Mike Blake/Reuters)





Campaign workers at a local Hillary Clinton organizing office wait for U.S. Democratic presidential candidate Hillary Clinton to visit during a stop in San Diego, California, United States, June 2, 2016. (Photo by Mike Blake/Reuters)





A pinata of U.S. Republican presidential candidate Donald Trump hangs outside offices for U.S. Democratic presidential candidate and U.S. Senator Bernie Sanders in Taos, New Mexico, U.S. June 2, 2016. (Photo by Brian Snyder/Reuters)





A demonstrator chants in protest against Republican U.S. presidential candidate Donald Trump outside his campaign event in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





A supporter for Republican U.S. presidential candidate Donald Trump (L) exchange words with a demonstrator during a campaign rally in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





A woman falls as police officers move the line during a demonstration against Republican U.S. presidential candidate Donald Trump outside his campaign event in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





A woman falls as police officers move the line during a demonstration against Republican U.S. presidential candidate Donald Trump outside his campaign event in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





A supporter (C) of Republican U.S. presidential candidate Donald Trump collides with another man after he was confronted by demonstrators outside a campaign rally in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





Demonstrators chant around a car during a demonstration against Republican U.S. presidential candidate Donald Trump after his campaign rally in San Jose, California, U.S. June 2, 2016. (Photo by Stephen Lam/Reuters)





Pins supporting Republican Presidential candidate Donald Trump, including one that reads “Hot chicks for Trump” are seen for sale at a campaign rally on June 1, 2016 in Sacramento, California. Donald Trump is campaigning in California ahead of the states June 7th Republican primary. (Photo by Elijah Nouvelage/Getty Images)





A supporter looks on as Democratic presidential candidate, U.S. Sen. Bernie Sanders (D-VT) speaks during a panel with Asian-Americans and Pacific Islanders at Cubberley Community Center on June 1, 2016 in Palo Alto, California. With less than a week to go before the California presidential primary, Sanders is campaigning in northern California. (Photo by Justin Sullivan/Getty Images)





A woman wearing a Trump shirt (C) is pelted with eggs by protesters while pinned against a door near where Republican presidential candidate Donald Trump holds a rally in San Jose, California on June 02, 2016. Protesters attacked Trump supporters as they left the rally, burned an american flag, trump paraphernalia and scuffled with police and each other. (Photo by Josh Edelson/AFP Photo)





A woman wipes egg off her face after being pursued by protesters while leaving Republican presidential candidate Donald Trump's campaign rally on Thursday, June 2, 2016, in San Jose, Calif. A group of protesters attacked Trump supporters who were leaving the presidential candidate's rally in San Jose on Thursday night. A dozen or more people were punched, at least one person was pelted with an egg and Trump hats grabbed from supporters were set on fire on the ground. (Photo by Noah Berger/AP Photo)