Democratic presidential candidate Bernie Sanders addresses a rally Wednesday at the Santa Clara County Fairgrounds in San Jose, Calif. The senator's campaign is intently focused on a big win in the state on June 7, and has poured money into TV ads there. Josh Edelson/AFP/Getty Images hide caption

toggle caption Josh Edelson/AFP/Getty Images

Donald Trump arrives at the Republican National Committee headquarters on Capitol Hill last week to meet with House Speaker Paul Ryan and other GOP leaders. Nicholas Kamm/AFP/Getty Images hide caption

toggle caption Nicholas Kamm/AFP/Getty Images
'Highly Sophisticated Killers' No More. Trump Embraces Big Donors
  • Download
  • <iframe src="https://www.npr.org/player/embed/478560644/478571309" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A voter enters a polling place on May 3 in Whiting, Ind. Older voters feel that the issues that concern them haven't been mentioned enough on the campaign trail. Scott Olson/Getty Images hide caption

toggle caption Scott Olson/Getty Images
Older Voters To Candidates: Don't Forget About Us
  • Download
  • <iframe src="https://www.npr.org/player/embed/478410141/478562686" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A demonstrator holds a "Stop Trump 2016" sign across the street from an April 25 Donald Trump rally, in West Chester, Pa. Bloomberg/Bloomberg via Getty Images hide caption

toggle caption Bloomberg/Bloomberg via Getty Images
Progressive SuperPACs Ramp Up Their Big-Money Effort Against Donald Trump
  • Download
  • <iframe src="https://www.npr.org/player/embed/477758538/477758539" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

Democratic presidential candidate Bernie Sanders waves to the crowd after arriving Tuesday at a campaign rally at the Big Four Lawn Park in Louisville, Ky. John Sommers II/Getty Images hide caption

toggle caption John Sommers II/Getty Images
Bernie Sanders Says He's Staying In And It's 'Good For The Democratic Party'
  • Download
  • <iframe src="https://www.npr.org/player/embed/476766494/476844451" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A supporter of Democratic presidential candidate Hillary Clinton wears campaign buttons as she listens to former President Bill Clinton at an event in Indiana. Joe Raedle/Getty Images hide caption

toggle caption Joe Raedle/Getty Images

Vice President Hubert Humphrey (right) and his running mate, Sen. Edmund S. Muskie, wave to the crowd with their wives at the Democratic Convention in Chicago on Aug. 29, 1968. Violence ensued inside and outside the convention hall. AP hide caption

toggle caption AP