Republican U.S. presidential candidate and New Jersey Governor Chris Christie shakes hands with supporters after formally announcing his campaign for the 2016 Republican presidential nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid 

Republican U.S. presidential candidate and New Jersey Governor Chris Christie gets a kiss from a supporter after he formally announced his campaign for the 2016 Republican presidential nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid TPX IMAGES OF THE DAY

Republican U.S. presidential candidate and New Jersey Governor Chris Christie formally announces his campaign for the 2016 Republican presidential nomination as his son Patrick looks on during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid 

A supporter uses his phone ahead of Republican U.S. presidential candidate and New Jersey Governor Chris Christie's formal announcement of his campaign for the 2016 Republican presidential nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid 

Republican U.S. presidential candidate and New Jersey Governor Chris Christie arrives on stage to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid 

Republican U.S. presidential candidate and New Jersey Governor Chris Christie waves after formally announcing his campaign for the 2016 Republican presidential nomination during a kickoff rally at Livingston High School in Livingston, New Jersey, June 30, 2015. REUTERS/Brendan McDermid (TPX IMAGES OF THE DAY)

New Jersey Governor Chris Christie, potential Republican presidential candidate, speaks at the Southern Republican Leadership Conference in Oklahoma City, Oklahoma May 22, 2015. REUTERS/Rick Wilking 

Potential 2016 Republican presidential candidate and New Jersey Governor Chris Christie delivers a speech about foreign policy in Portsmouth, New Hampshire May 18, 2015. REUTERS/Brian Snyder TPX IMAGES OF THE DAY

New Jersey Governor Chris Christie speaks at the New Hampshire Institute of Politics in Manchester, New Hampshire April 14, 2015. REUTERS/Dominick Reuter 

Governor of New Jersey Chris Christie arrives to speak at the Freedom Summit in Des Moines, Iowa, January 24, 2015. REUTERS/Jim Young (UNITED STATES - Tags: POLITICS) 

New Jersey Governor Chris Christie greets a member of the assembly as he arrives for his annual State of the State address in Trenton, New Jersey January 14, 2014. Christie opened his State of the State Address on Tuesday with an apology and a vow to fully cooperate with "all appropriate" investigations of an apparent scheme to cause massive traffic jams as well as the use of federal money for a state ad campaign. REUTERS/Lucas Jackson (UNITED STATES - Tags: POLITICS) 

New Jersey Governor Chris Christie speaks during his annual State of the State address in Trenton, New Jersey January 14, 2014. Christie opened his State of the State Address on Tuesday with an apology and a vow to fully cooperate with "all appropriate" investigations of an apparent scheme to cause massive traffic jams as well as the use of federal money for a state ad campaign. REUTERS/Lucas Jackson (UNITED STATES - Tags: POLITICS) 

New Jersey Governor Chris Christie gives a news conference in Trenton January 9, 2014. Christie on Thursday fired a top aide at the center of a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge to settle a political score. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS) 

New Jersey Governor Chris Christie reacts during a news conference in Trenton January 9, 2014. Christie on Thursday fired a top aide at the center of a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge to settle a political score. Christie told a news conference he was stunned and heartbroken by revelations that his staff was behind the traffic jam designed to punish a local mayor who declined to endorse Christie's re-election bid. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS TPX IMAGES OF THE DAY) 

New Jersey Governor Chris Christie gives a news conference in Trenton January 9, 2014. Christie on Thursday fired a top aide at the center of a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge to settle a political score. Christie told a news conference he was stunned and heartbroken by revelations that his staff was behind the traffic jam designed to punish a local mayor who declined to endorse Christie's re-election bid. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS TPX IMAGES OF THE DAY) 

New Jersey Governor Chris Christie gives a news conference in Trenton January 9, 2014. Christie on Thursday fired a top aide at the center of a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge to settle a political score. Christie told a news conference he was stunned and heartbroken by revelations that his staff was behind the traffic jam designed to punish a local mayor who declined to endorse Christie's re-election bid. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS HEADSHOT) 

New Jersey Governor Chris Christie (L) departs City Hall in Fort Lee, New Jersey January 9, 2014. Christie met with the mayor of Fort Lee to discuss a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge in September to settle a political score. Christie said at a separate news conference he was stunned and heartbroken by revelations that his staff was behind the traffic jam designed to punish Sokolich who declined to endorse Christie's re-election bid. REUTERS/Lucas Jackson (UNITED STATES - Tags: POLITICS TPX IMAGES OF THE DAY) 

New Jersey Governor Chris Christie speaks to the media as he leaves city hall in Fort Lee, New Jersey January 9, 2014. Christie on Thursday fired a top aide at the center of a brewing scandal that public officials orchestrated a massive traffic snarl on the busy George Washington Bridge to settle a political score. Christie said at a news conference he was stunned and heartbroken by revelations that his staff was behind the traffic jam designed to punish Fort Lee mayor Mark Sokolich who declined to endorse Christie's re-election bid. REUTERS/Eric Thayer (UNITED STATES - Tags: POLITICS) 

Republican New Jersey Governor Chris Christie gestures as he takes the stage at his election night party in Asbury Park, New Jersey November 5, 2013. Christie won re-election in a landslide on Tuesday, a victory seen boosting his widely expected bid for the White House in 2016. REUTERS/Mike Segar (UNITED STATES - Tags: POLITICS ELECTIONS) 

Republican New Jersey Governor Chris Christie addresses his supporters as he stands with his family at his election night party in Asbury Park, New Jersey November 5, 2013. Christie won re-election in a landslide on Tuesday, a victory seen boosting his widely expected bid for the White House in 2016. REUTERS/Mike Segar (UNITED STATES - Tags: POLITICS ELECTIONS) 

New Jersey Governor Chris Christie exits a polling station after casting his vote during the New Jersey governor election in Mendham Township, New Jersey, November 5, 2013. Christie was poised on Tuesday to win re-election by a landslide, the latest polls show, a first step on what is expected to be a far bumpier path in his likely bid for the White House in 2016. REUTERS/Eduardo Munoz (UNITED STATES - Tags: POLITICS ELECTIONS) 

New Jersey governor Chris Christie attends a statewide prayer service at The New Hope Baptist Church on the one-year anniversary of Superstorm Sandy in Newark, New Jersey on October 29, 2013. Superstorm Sandy left more then 100 people dead and caused tens of billions of dollars in damage. REUTERS/Eric Thayer (UNITED STATES - Tags: DISASTER ENVIRONMENT ANNIVERSARY) 

A resident kisses the hand of New Jersey Governor Chris Christie on the one-year anniversary of Hurricane Sandy in Union Beach, New Jersey on October 29, 2013. Hurricane Sandy, also known as Superstorm Sandy, left more than 100 people dead and caused tens of billions of dollars in damage. REUTERS/Eric Thayer (UNITED STATES - Tags: DISASTER POLITICS ENVIRONMENT ANNIVERSARY) 

New Jersey Governor Chris Christie speaks with first responders on the one-year anniversary of Hurricane Sandy in Sayreville, New Jersey October 29, 2013. Hurricane Sandy, also known as Superstorm Sandy, left more than 100 people dead and caused tens of billions of dollars in damage. REUTERS/Eric Thayer (UNITED STATES - Tags: DISASTER ENVIRONMENT ANNIVERSARY) 

Governor Chris Christie takes questions from the media following an announcement event about more funding to the New Jersey Institute of Technology in Newark, September 3, 2013. Christie is the Republican front-runner for the November 5, 2013 governors' election. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS HEADSHOT EDUCATION) 

New Jersey Governor Chris Christie throws out the ceremonial first pitch before the Little League World Series championship baseball game between Tokyo, Japan and Chula Vista, California in Williamsport, Pennsylvania August 25, 2013. REUTERS/Eduardo Munoz (UNITED STATES - Tags: SPORT BASEBALL POLITICS) 

New Jersey Governor Chris Christie introduces U.S. President Barack Obama (not pictured) to speak on the rebuilding of the Jersey Shore following Hurricane Sandy, from Asbury Park in New Jersey, May 28, 2013. President Barack Obama and Christie teamed up again to tour areas damaged by last year's Hurricane Sandy, giving a boost to a Democratic president enmeshed in scandals at home. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS HEADSHOT) 

Britain's Prince Harry (R) walks with New Jersey Governor Chris Christie as they view areas of the boardwalk that have been repaired in Seaside Heights, a beach town hit by Hurricane Sandy last year, in New Jersey, May 14, 2013. REUTERS/Lucas Jackson (UNITED STATES - Tags: ROYALS POLITICS DISASTER) 

New Jersey Governor Chris Christie speaks at a groundbreaking ceremony for the Technology Enhanced Accelerated Learning Center news conference in Newark, New Jersey, May 7, 2013. Christie, who has struggled with obesity for much of his adult life, said on Tuesday he underwent lap band surgery in February to lose weight, a move he said had nothing to do with a possible run for the White House in 2016. REUTERS/Lucas Jackson (UNITED STATES - Tags: POLITICS HEALTH) 

New Jersey Governor Chris Christie gives his State of the State address in the assembly chamber in Trenton, New Jersey, January 8, 2013. Christie renewed his calls to the U.S. Congress on Tuesday to quickly pass the full $60.4 billion Superstorm Sandy relief package, saying victims in New Jersey had been short-changed. Talking behind Christie are Assembly Speaker Sheila Oliver (left) and Senate President Stephen Sweeney. REUTERS/Carlo Allegri (UNITED STATES - Tags: POLITICS) 

U.S. President Barack Obama speaks in a neighborhood after he tours damage done by Hurricane Sandy in Brigantine, New Jersey, October 31, 2012. New Jersey Governor Chris Christie stands behind Obama. REUTERS/Larry Downing (UNITED STATES - Tags: POLITICS DISASTER) 

U.S. President Barack Obama (R) is greeted by New Jersey Governor Chris Christie after he arrives at Atlantic City International Airport in New Jersey before surveying Hurricane Sandy damage, October 31, 2012. REUTERS/Larry Downing (UNITED STATES - Tags: POLITICS DISASTER) 

New Jersey Governor Chris Christie delivers the keynote address during the second session of the Republican National Convention in Tampa, Florida, August 28, 2012 REUTERS/Mike Segar (UNITED STATES - Tags: POLITICS ELECTIONS)

New Jersey Governor Chris Christie points out into the crowd after delivering the keynote address during the second session of the Republican National Convention in Tampa, Florida August 28, 2012. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS ELECTIONS)

Governor of New Jersey Chris Christie and his wife Mary Pat Christie attend the Allen & Co Media Conference in Sun Valley, Idaho July 13, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: MEDIA POLITICS)