Scott Walker's White House run

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker waves a U.S. one dollar bill as he formally announces his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker arrives on stage to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker shakes hands with supporters as he arrives on stage to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Jim Young

Wisconsin Governor Scott Walker watches his wife Tonette address the crowd as he stands backstage looking at a TV monitor before going out to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Jim Young

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker formally announces his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Jim Young

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker arrives on stage to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

A supporter of U.S. Republican presidential candidate and Wisconsin Governor Scott Walker arrives for his campaign kickoff rally in Waukesha, Wisconsin, United States, July 13, 2015. REUTERS/Jim Young

U.S. Republican presidential candidate and Wisconsin Governor Scott Walker poses with his son Alex (L), his wife Tonette and his son Matthew (R) as he arrives on stage to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

A campaign worker hands out small U.S. flags to supporters waiting for U.S. Republican presidential candidate and Wisconsin Governor Scott Walker to formally announce his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Jim Young

A protestor holds up a sign ahead of U.S. Republican presidential candidate and Wisconsin Governor Scott Walker's formal announcement of his campaign for the 2016 Republican presidential nomination, during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

Supporters bow their heads in prayer before U.S. Republican presidential candidate and Wisconsin Governor Scott Walker formally announces his campaign for the 2016 Republican presidential nomination during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Jim Young

Protestors hand out signs ahead of U.S. Republican presidential candidate and Wisconsin Governor Scott Walker's formal announcement of his campaign for the 2016 Republican presidential nomination, during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

Protestors await U.S. Republican presidential candidate and Wisconsin Governor Scott Walker's formal announcement of his campaign for the 2016 Republican presidential nomination, during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck

Workers hang a sign for U.S. Republican presidential candidate and Wisconsin Governor Scott Walker's campaign kickoff rally in Waukesha, Wisconsin, United States, July 13, 2015. REUTERS/Jim Young

Protestors holds up signs ahead of U.S. Republican presidential candidate and Wisconsin Governor Scott Walker's formal announcement of his campaign for the 2016 Republican presidential nomination, during a kickoff rally in Waukesha, Wisconsin, July 13, 2015. REUTERS/Darren Hauck