(FILES) This file photo taken on June 29, 2016 shows US Senator Elizabeth Warren, Democrat of Massachusetts, speaking in Washington, DC. US Democratic presidential candidate Clinton is expected to reveal her vice presidential pick by July 23, 2016, when she campaigns in Florida. The feisty senator is a liberal superstar who can help transfer the Sanders allegiance to Clinton. Warren has developed a reputation for ripping into Trump at every opportunity. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images