(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