What he does now: Governor of Wisconsin
What he used to do: Walker has spent the majority of his career holding public office. First elected to the Wisconsin State Assembly in 1993, Walker served several terms in the state legislature before being elected Milwaukee County Executive in 2002. In 2010, he was elected to his first term as governor and withstood a 2012 recall election that followed Walker's controversial reforms to strip the state's public unions of most of their collective bargaining powers. The only governor in U.S. history to survive a recall election, Walker won in 2012 by a larger margin than in 2010. He was re-elected to a second term in 2014.
Declared as a candidate: July 13.
In his own words: "It's one thing to fight. A lot of people are good at fighting. We're good at fighting and winning."
Family tree: Walker is the son of a now-retired Baptist preacher and his mother worked as a secretary, both of whom are still alive. He has one younger brother. Walker and his wife, Tonette, who is 12 years his senior, have been married for 22 years and have two college-age sons. Their eldest son, Matt, attends Marquette University where Walker also attended college for three years before dropping out. His younger son, Alex, attends the University of Wisconsin, Madison. Both sons are expected to take time off from college to help their father campaign.
He's the son of a: Preacher. Walker, 47, was born in Colorado Springs, Colorado and spent the early years of his childhood in Plainfield, Iowa, where his father served as a preacher at a local Baptist church. Walker has compared growing up as the son of a preacher to living in a fishbowl and said the experience prepared him for public life. When Walker was 10, his family moved to Delavan, Wisconsin, where Walker attended high school and participated in a number of organized activities, ranging from track to playing drums in the marching band. He was also active in Boy Scouts growing up and obtained the rank of an Eagle Scout.
Something he didn't finish: College. Walker attended Marquette University in Milwaukee. In his junior year, he made an unsuccessful run for student government president. He dropped out of school before completing his senior year, instead taking a full-time job with the Red Cross. If he were to win the White House, Walker would become the first president since Harry Truman -- elected over 70 years ago -- to lack a college degree.
Breakout moment in politics: 2011 was the year that launched Walker's rise to political stardom. He famously faced off against thousands of pro-union protesters, many of whom camped out at the state capitol for a time, to oppose Walker's proposed Act 10, which called for most public employees to pay for a larger share of their pensions and healthcare costs, while curtailing collective bargaining powers. Despite the protests and efforts by Democrats to block the legislation, Walker ultimately signed the bill into law. Walker's opponents subsequently tried to unseat him, collecting enough signatures to prompt a recall election. Walker prevailed in the election, winning by a larger margin than he did in 2010.
What you might not know about him: He's the proud owner of a 2003 Harley Davidson Road King and has plans to take his bike out on the campaign trail.
Food he can’t live without: Walker is a big fan of barbecue. He even met his wife at a local Wisconsin barbecue joint, Saz's, and brought her back to the same spot several months later to propose. The couple continues to make it a tradition to revisit Saz's to celebrate their anniversary.
Might have wished for a do-over: The most embarrassing moment of Walker's political career came when he took a prank call from an advocacy journalist posing as conservative mega-donor David Koch. On the call, which was recorded, Walker said he had considered sending "troublemakers" into the crowd of pro-union protesters opposing his controversial Act 10. Walker has since called the moment a "a turning point," writing in his memoir, "Unintimidated: A Governor's Story and A Nation's Challenge," that the embarrassing episode "helped me stay focused on the people I was elected to serve, and reminded me of God’s abundant grace and the paramount need to stay humble.”
What could hold him back: Having only served at the state and local level, Walker’s lack of foreign policy experience is regarded as one of his greatest weaknesses going into the 2016 election. He also faces the challenge of balancing his appeal to conservative and Evangelical voters on social issues while staying moderate enough to appeal in a general election and will face scrutiny for having shifted his position on a number of issues, ranging from immigration reform to abortion and same-sex marriage, in recent years.