Brooke Peterson poses for photos with a sign at a rally for Democratic presidential candidate Sen. Bernie Sanders, I-Vt., on Tuesday in Carson, Calif. Jae C. Hong/AP hide caption
Donald Trump is introduced by National Rifle Association executive director Chris Cox (left) and NRA executive vice president Wayne LaPierre on Friday at the organization's convention in Louisville, Ky. Mark Humphrey/AP hide caption
The NPR Politics team tapes its podcast in front of a studio audience at NPR headquarters in Washington, D.C. Meg Kelly/NPR hide caption
Republican presidential candidate Donald Trump speaks during his rally at the Charleston Civic Center on May 5 in Charleston, W.Va. Mark Lyons/Getty Images hide caption
Likely Republican presidential nominee Donald Trump speaks during a rally in Eugene, Ore. Ted S. Warren/AP hide caption
Democratic presidential candidate Bernie Sanders shakes hands with supporters in January in New York City. Andrew Burton/Getty Images hide caption
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
Ships transporting containers like these at the Port of Tacoma, Washington, last year carry the goods at issue in the TPP deal. A new report says the trade pact would boost the U.S. economy, but only by a modest amount. Ted S. Warren/AP hide caption
Two women cast their ballots for Republican candidates during the state's Republican caucuses on March 5 in Wichita, Kan. Getty Images hide caption
Fox aired an interview with anchor Megyn Kelly and apparent GOP presidential nominee Donald Trump on Tuesday night. Victoria Will/AP hide caption
Democratic presidential candidate Bernie Sanders waves as he walks onto the stage during a rally Tuesday in Carson, Calif. Jae C. Hong/AP hide caption
The early morning sun rises behind the U.S. Supreme Court building on May 15. Mark Wilson/Getty Images hide caption
Warehouse employee Rejinaldo Rosales, 34, at work in Tracy, Calif. Brandon Bailey/AP hide caption
Democratic presidential candidate Bernie Sanders says his campaign and supporters were not treated fairly during last Saturday's Nevada Democratic convention. Charlie Neibergall/AP hide caption
Donald Trump greets supporters after a campaign in Wilkes-Barre, Pa., last month. Mel Evans/AP hide caption
Hillary Clinton, then secretary of state, greets troops in Kabul, Afghanistan, in 2012. She logged nearly a million miles visiting 112 countries in that position. Brendan Smialowski/AP hide caption
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
Apparent Republican nominee Donald Trump has won more raw votes from 18-29 year olds this primary season than likely Democratic nominee Hillary Clinton, even though young voters lean Democratic. Scott Olson/Getty Images hide caption
Democratic Rep. Tammy Duckworth is running against Illinois Republican Sen. Mark Kirk. Kris Connor/Getty Images hide caption
The pastor of Fort Des Moines Church of Christ in Des Moines, Iowa, says Republican presidential candidate Donald Trump is "morally loathsome." Sarah McCammon/NPR hide caption
The seal of the Central Intelligence Agency at the lobby of the Original Headquarters Building at the CIA headquarters in McLean, Va. Alex Wong/Getty Images hide caption
President Obama has delivered nearly two dozen commencement speeches during his time in office — including this one, at the University of California, Irvine, in 2014. Jim Watson/AFP/Getty Images hide caption
President Obama speaks during Rutgers University's 250th anniversary commencement ceremony on Sunday in New Brunswick, N.J. Evan Vucci/AP hide caption