(FILES) This file photo taken on January 21, 2016 shows US Labor Secretary Tom Perez speaking in Washington, DC. US Democratic presidential candidate Clinton is expected to reveal her vice presidential pick by July 23, when she campaigns in Florida. One of the true liberals on the shortlist, Perez could rally core Democrats and heal the rift with leftwing supporters of Clinton's former nomination rival Bernie Sanders. As a Latino in the cabinet, he could cement the increasingly important Hispanic vote. / AFP PHOTO / Nicholas KammNICHOLAS KAMM/AFP/Getty Images

WASHINGTON, DC - JULY 21: U.S. President Barack Obama (C) holds a jersey given to him by the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year at the White House July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images) *** BESTPIX ***

US President Barack Obama shows a jersey presented to him by Kansas City Royals Manager Ned Yost (R) during an event honoring 2015 World Series champions the Kansas City Royals on July 21, 2016 in the East Room of the White House in Washington, DC. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

WASHINGTON, DC - JULY 21: U.S. President Barack Obama (C) holds a jersey given to him by the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year at the White House July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - JULY 21: U.S. President Barack Obama (L), is given a jersey by Manager Ned Yost (R), of the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year, at the White House, July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - JULY 21: U.S. President Barack Obama (C) holds a jersey given to him by the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year at the White House July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - JULY 21: U.S. President Barack Obama (C) holds a jersey given to him by the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year at the White House July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images)

WASHINGTON, DC - JULY 21: US President Barack Obama (R), acknowledges Hall Of Famer George Brett (C), VP of Baseball Operations for the MLB 2015 World Series Champion Kansas City Royals during an event to honor them for their winning season last year, at the White House, July 21, 2016 in Washington, DC. (Photo by Mark Wilson/Getty Images)