Republican U.S. presidential nominee Donald Trump holds a campaign rally at the ​Ziegler Building at the Washington County Fair Park & Conference Center in West Bend, Wisconsin August 16, 2016. REUTERS/Eric Thayer

Republican Governor Dennis Daugaard of South Dakota listens to remarks during a "Growth and Jobs in America" discussion at the National Governors Association Winter Meeting in Washington, February 23, 2014. REUTERS/Mike Theiler

Governor Terry Branstad of Iowa attends a meeting with Chinese President Xi Jinping and four other United States governors to discuss clean technology and economic development in Seattle, Washington September 22, 2015. REUTERS/Matt Mills McKnight

(FILES) This file photo taken on February 7, 2013 shows former Interior Secretary Ken Salazar as he speaks during the National Prayer Breakfast in Washington, DC. Hillary Clinton on August 16, 2016 announced the formation of a transition team to handle the transfer of power at the White House if the Democratic candidate is elected to succeed President Barack Obama. Ken Salazar, a former secretary of the interior and Colorado senator, will head the team as part of the traditional preparations ahead of the November 8 elections, her campaign said. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

Republican Governor Pat McCrory of North Carolina makes remarks during a "Growth and Jobs in America" discussion at the National Governors Association Winter Meeting in Washington, February 23, 2014. REUTERS/Mike Theiler

Republican Governor Pat McCrory of North Carolina makes remarks during a "Growth and Jobs in America" discussion at the National Governors Association Winter Meeting in Washington, February 23, 2014. REUTERS/Mike Theiler

U.S. Vice President Joe Biden delivers remarks at a conference of the Center for New American Security think tank in Washington U.S., June 20, 2016. REUTERS/Carlos Barria

The headquarters of the Democratic National Committee is seen in Washington, U.S. June 14, 2016. REUTERS/Gary Cameron