Donald Trump hugs a U.S. flag as he takes the stage for a campaign town hall meeting in Derry, New Hampshire, August 19, 2015. REUTERS/Brian Snyder

Hillary Clinton greets Louie Dixon as she campaigns at the Iowa State Fair in Des Moines, Iowa, August 15, 2015. REUTERS/Jim Young

Jeb Bush shares a laugh with attendees at the Iowa State Fair in Des Moines, Iowa, August 14, 2015. REUTERS/Jim Young

Donald Trump poses with policemen, as he departs Laredo, Texas July 23, 2015. REUTERS/Rick Wilking

Scott Walker drinks a glass of beer during a campaign stop at the Billy Goat Tavern in Chicago, Illinois, United States, July 27, 2015. REUTERS/Jim Young

Hillary Clinton answers a reporter's question in front of a sign reading "Pant Suit Power" following a town hall campaign stop in Nashua, New Hampshire July 28, 2015. REUTERS/Brian Snyder

Rand Paul holds thousands of signatures from supporters of defunding Planned Parenthood during a rally at Capitol Hill in Washington July 28, 2015. REUTERS/Carlos Barria

A bus promoting Bernie Sanders is seen after a campaign town hall in Manchester, New Hampshire, August 1, 2015. REUTERS/Dominick Reuter

Jeb Bush listens to a question from the audience during a town hall meeting campaign stop at the Medallion Opera House in Gorham, New Hampshire July 23, 2015. REUTERS/Brian Snyder

Hillary Clinton answers questions from reporters following a campaign town hall meeting in Dover, New Hampshire, July 16, 2015. REUTERS/Brian Snyder

Lindsey Graham gestures with Arizona Senator and 2008 Republican presidential nominee John McCain at a campaign town hall event in Manchester, New Hampshire, August 1, 2015. REUTERS/Dominick Reut

Scott Walker's Winnebago drives over a dirt road on his way to a campaign stop in Haverhill, Iowa, July 18, 2015. REUTERS/Jim Young

"Brownie" wears stickers for Jeb Bush before a campaign stop at the Original Lahout's Country Clothing and Ski Shop in Littleton, New Hampshire July 23, 2015. REUTERS/Brian Snyder

Jeb Bush poses for a photograph with a group of day care children during a campaign stop in Lancaster, New Hampshire, July 23, 2015. REUTERS/Brian Snyder

Ted Cruz gestures as he engages in a lengthy debate on the Iran nuclear deal with Code Pink peace activism group co-founder Medea Benjamin (L with peace sign) in Lafayette Park across from the White House, July 23, 2015. REUTERS/Jim Bourg

Hillary Clinton looks around a post to greet audience members at a campaign launch party at Carter Hill Orchard in Concord, New Hampshire, June 15, 2015. REUTERS/Brian Snyder

Bobby Jindal wears cowboy boots at the Family Leadership Summit in Ames, Iowa, July 18, 2015. REUTERS/Jim Young

A supporter holds a sign at a rally for Bernie Sanders in Dallas, Texas July 19, 2015. REUTERS/Mike Stone

Rand Paul listens to his introduction during a campaign stop at Royal Kitchen and Bathroom Cabinets in Niles, Illinois, United States, August 1, 2015. REUTERS/Jim Young

Hillary Clinton speaks during a campaign stop at Beech Hill Farm in Hopkinton, New Hampshire July 28, 2015. REUTERS/Brian Snyder

Rick Perry bends down to shake hands with an audience member as fellow candidate John Kasich looks on after the conclusion of the Voters First Presidential Forum in Manchester, New Hampshire August 3, 2015. REUTERS/Brian Snyder

Rick Santorum sits between fellow candidates Scott Walker and George Pataki as he waits his turn to speak during the Voters First Presidential Forum in Manchester, New Hampshire August 3, 2015. REUTERS/Brian Snyder

Bernie Sanders listens to remarks at the Iowa Democratic Party's Hall of Fame dinner in Cedar Rapids, Iowa, July 17, 2015. REUTERS/Jim Young

Donald Trump arrives for a news conference at the Family Leadership Summit in Ames, Iowa, July 18, 2015. REUTERS/Jim Young

Sisters Sophia (L) and Norah Boice of North Charleston play on seats after Hillary Clinton spoke at a rally at Trident Technical College Conference Center in North Charleston, South Carolina, June 17, 2015. REUTERS/Randall Hill

Supporters of Scott Walker line up to attend a campaign stop in Davenport, Iowa, July 17, 2015. REUTERS/Jim Young

Rick Perry adjusts his tie as he listens to his introduction from the side of the stage at the Freedom Summit in Des Moines, January 24, 2015. REUTERS/Jim Young

Lindsey Graham holds up his beer after speaking during a campaign stop at Milly's Tavern in Manchester, New Hampshire, July 10, 2015. REUTERS/Brian Snyder

A sign guides guests to a town hall campaign stop with Jeb Bush at the VFW Post in Hudson, New Hampshire, July 8, 2015. REUTERS/Brian Snyder

Supporters of Jeb Bush knock on doors of the auditorium to gain entrance to his formal announcement of his campaign at a kickoff rally in Miami, June 15, 2015. REUTERS/Carlo Allegri

Marco Rubio autographs a magazine with his picture on the cover after he announced his bid for the Republican nomination during a speech at Freedom Tower in Miami, April 13, 2015. REUTERS/Carlo Allegri

Assorted cookies in support of Rick Perry are seen at a National Press Club luncheon in Washington, July 2, 2015. REUTERS/Yuri Gripas

An attendee arrives at a campaign event for Bernie Sanders in Des Moines, Iowa, June 12, 2015. REUTERS/Jim Young

Hillary Clinton adjusts her make-up before speaking at the Iowa Democratic Party's Hall of Fame dinner in Cedar Rapids, Iowa, July 17, 2015. REUTERS/Jim Young

Jeb Bush runs along the Independence Day parade route in Amherst, New Hampshire, July 4, 2015. REUTERS/Gretchen Ertl

A man waits for the start of a town-hall style campaign stop with Rand Paul in Londonderry, New Hampshire, May 11, 2015. REUTERS/Brian Snyder

Chris Christie gets a kiss from a supporter after he formally announced his campaign for the Republican nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid

Supporters of Donald Trump wait to see their candidate at a campaign event in Laconia, New Hampshire, July 16, 2015. REUTERS/Dominick Reuter

A Jewish supporter of Hillary Clinton shows off his "Hillary" inscribed yarmulke skullcap before her campaign kick off rally in Franklin D. Roosevelt Four Freedoms Park on Roosevelt Island in New York City, June 13, 2015. REUTERS/Brendan McDermid