House Democratic Caucus Chair Xavier Becerra hugs Democratic presidential candidate Hillary Clinton (C) as Minority Leader Nancy Pelosi(R) looks on as Clinton arrives for a meeting with the House Democratic Caucus on June 22, 2016 at the US Capitol in Washington, DC. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

WASHINGTON, DC - JUNE 22: Accompanied by House Minority Leader Rep. Nancy Pelosi (D-CA) (L), Democratic presidential candidate Hillary Clinton arrives to meet with House Democrats June 22, 2016 on Capitol Hill in Washington, DC. Clinton joined the House Democratic Caucus meeting as she continued to campaign for the election. (Photo by Alex Wong/Getty Images)

WASHINGTON, DC - JUNE 22: Democratic presidential candidate Hillary Clinton (C) is greeted by House Democratic Caucus Chair Xavier Becerra (D-CA) (L) as House Minority Leader Rep. Nancy Pelosi (D-CA) (R) looks on as she arrives to meet with House Democrats June 22, 2016 on Capitol Hill in Washington, DC. Clinton joined the House Democratic Caucus meeting as she continued to campaign for the election. (Photo by Alex Wong/Getty Images)

Democratic presidential candidate Hillary Clinton arrives for a meeting with the House Democratic Caucus on June 22, 2016 at the US Capitol in Washington, DC. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

Democratic presidential candidate Hillary Clinton arrives for a meeting with the House Democratic Caucus on June 22, 2016 at the US Capitol in Washington, DC. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

Democratic presidential candidate Hillary Clinton arrives for a meeting with the House Democratic Caucus on June 22, 2016 at the US Capitol in Washington, DC. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

(FILES) This file photo taken on June 13, 2016 shows people gather to protest gun violence and call for sensible gun laws outside the White House in Washington, DC. The Republican-controlled US Senate rejected four competing gun control measures June 20, 2016 just days after the Orlando club massacre, highlighting the partisan feuding over an issue set to resonate during a heated presidential election year. With a month to go before Republicans and Democrats formally nominate their White House hopefuls, lawmakers failed to compromise on one of the most sensitive hot-button issues in America. Even as they sought to appear keen to take action following the deadliest mass shooting in US history that left 49 dead at a gay nightclub in Orlando a week ago, Republicans and Democrats voted down four amendments -- two from each party -- that would have limited some gun purchases, including those by suspected terrorists. / AFP PHOTO / MOLLY RILEYMOLLY RILEY/AFP/Getty Images

Landing markers are moved for placment on the South Lawn ahead of the return of Marine One and US President Barack Obama to the White House on June 21, 2016 in Washington, DC. Obama returned to the White House after a trip to the Walter Reed National Military Medical Center to visit wounded service members. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images