Could union-busting Scott Walker be the next president?

As the Republican field for president gets increasingly crowded, one late entry has the possibility of being a strong contender for the nomination. Scott Walker is little known across the US - so why is he a frontrunner?

For those feeling less than inspired by the prospect of another Bush-Clinton face-off for the presidency in 2016, there's one man in particular who has the potential to ruin that scenario.

Meet Scott Kevin Walker - the Republican governor of the Midwest state of Wisconsin who is set to announce his presidential bid on Monday.

Over the past few months, the 47-year-old, Harley-Davidson-riding governor has become something of a poster child for conservatives and come from nowhere in the polls to join former Florida Governor Jeb Bush and Florida Senator Marco Rubio among the top tier of candidates.

Not only has he pleased business groups by pushing through laws dismantling collective bargaining and automatic deduction of union dues, but he has taken a hard line on social issues too, such as abortion, making him attractive to core conservatives who tend to be further to the right.

Walker sits for an interview before taking to his motorcycle for a political event

"He's sort of the one person in the field that can play in both lanes," said Bill McCoshen, a political consultant in Wisconsin who knows Walker well.

"He can be in the establishment lane and he can also be on the anti-establishment side; and you know most people expected Jeb Bush to take the establishment vote and there would be somebody else in the anti-establishment lane - Walker is sort of creating problems for everybody."

Republicans also like him because he is a winner. When he took on the unions in Wisconsin, he faced 100,000 angry protestors at the state capitol.

"We hadn't seen anything like that in Madison since the Vietnam War protests," said Jason Stein, a reporter for the Milwaukee Journal Sentinel and author of a book on Walker.

"It was just a sea or a lake of humanity... you had every floor space, practically, covered with people, I mean there were times when you couldn't see the flagstones at all. It was exceptional, it was unprecedented."

Walker's time as governor of Wisconsin has won him national admirers and national critics

Denise Ehron, an administrator at the University of Wisconsin, was one of the many who opposed Walker. Standing in her backyard in the city of Whitewater the anger is still fresh. She says the reforms saw her household income drop by 14%.

"We had just bought a house a couple of years before that so we had a mortgage that we hadn't had before," Ehron said.

"But also just by being union members it became a bad word on campus, and in the town and in the state, and if you said you were a union member, 'Oh, oh you're a public employee? Ooh that's nasty'. Just morale-wise was really hard to take."

Walker faced the protestors down and subsequently won a recall election - no easy feat in a swing state like Wisconsin.

But if his opponents are numerous so are his supporters.

Sitting in a diner next to Marquette University in Milwaukee, Katie Flannigan spreads out her scrapbooks from her student days there.

They are stuffed full of cuttings, leaflets and notes from her time running Walker's campaign for student president. One badge reads "beam me up Scotty".

"Whoever is president has to be human, and he is such a kind person and fair person… sure he looks the part of a politician, but he is not anybody that would say one thing and do another," Flannigan said.

"I would bet my house on that. He's just a good hearted person."

Thousands took to the state capitol in opposition to a Walker-supporter bill that cut collective bargaining rights

"I think what's changed about him is less hair and he's added country music to his playlist."

Walker failed to win that student election - one of a very few electoral setbacks in his political career. He dropped out of school shortly after. If he became president, it would make him the first leader without a college degree since Harry Truman.

His entry into the crowded Republican presidential field has not been without problems.

At a big conservative conference in Washington in February, he sent his communications team into damage-control mode after suggesting he would be able to cope with the threat from the so-called Islamic State, given how he handled 100,000 protestors in Wisconsin.

Governor Walker "was in no way comparing any American citizen to IS," a spokeswoman told reporters in a hurried statement.

Walker then survived a recall election

He has also faltered on foreign affairs more generally - batting questions away on a trip to London when asked his views.

He does appear to be holding up, however, and significantly seems to have the fundraising ability to stay the course.

"The recall in 2012 is the gift that keeps on giving" said Charles Franklin, a professor at Marquette and director of the Marquette Law School poll which has been tracking Walker's appeal.

"The special election allowed him to raise unlimited donations…from over 300,000 donors."

And that, he said, gives Walker "solid potential".