WASHINGTON, DC - SEPTEMBER 13: U.S. Sen. Bernie Sanders (I-VT) (R) speaks during a rally against the Dakota Access Pipeline September 13, 2016 at Lafayette Square in Washington, DC. Activists held a rally calling on President Barack Obama to stop the Dakota Access Pipeline. (Photo by Alex Wong/Getty Images)

WASHINGTON, DC - SEPTEMBER 13: Dennis Zotigh (R) and his father Ralph Zotigh (L) of the Kiowa, Dakota, and Pueblo Tribes sing during a rally against the Dakota Access Pipeline September 13, 2016 at Lafayette Square in Washington, DC. Activists held a rally calling on President Barack Obama to stop the Dakota Access Pipeline. (Photo by Alex Wong/Getty Images)

WASHINGTON, DC - SEPTEMBER 13: U.S. Sen. Bernie Sanders (I-VT) (L) waits to be introduced during a rally against the Dakota Access Pipeline September 13, 2016 at Lafayette Square in Washington, DC. Activists held a rally calling on President Barack Obama to stop the Dakota Access Pipeline. (Photo by Alex Wong/Getty Images)

WASHINGTON, DC - SEPTEMBER 13: U.S. Sen. Bernie Sanders (I-VT) speaks during a rally against the Dakota Access Pipeline September 13, 2016 at Lafayette Square in Washington, DC. Activists held a rally calling on President Barack Obama to stop the Dakota Access Pipeline. (Photo by Alex Wong/Getty Images)

U.S. President Barack Obama meets with Israeli Prime Minister Benjamin Netanyahu in the Oval office of the White House in Washington November 9, 2015. REUTERS/Kevin Lamarque

WASHINGTON, DC - SEPTEMBER 13: U.S. Sen. Bernie Sanders (I-VT) (R) speaks during a rally against the Dakota Access Pipeline September 13, 2016 at Lafayette Square in Washington, DC. Activists held a rally calling on President Barack Obama to stop the Dakota Access Pipeline. (Photo by Alex Wong/Getty Images)

U.S. Representative Jeb Hensarling (R-TX) (C) arrives for a Republican caucus meeting at the U.S. Capitol in Washington, October 9, 2015. REUTERS/Jonathan Ernst

(FILES) This file photo taken on September 10, 2015 shows Bryan Pagliano, a former State Department employee who worked on former US Secretary of State and Democratic Presidential hopeful Hillary Clinton's private e-mail server, as he leaves after invoking his Fifth Amendment right against self-incrimination, before the House Select Committee on Benghazi, on Capitol Hill in Washington, DC. The former aide to Hillary Clinton who set up the controversial private email server she used while secretary of state ignored an order to testify on September 13, 2016 before a congressional committee. Bryan Pagliano's absence is likely to add fuel to a raging debate about Clinton's own transparency as she enters the final stretch of the US presidential elections. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images