US Republican Scott Walker joins White House race

WASHINGTON - Wisconsin Governor Scott Walker officially announced Monday he was joining the crowded field of Republicans jostling for their party's nomination as 2016 presidential candidate.

Walker, who earned national attention for his protracted battle with labor unions, announced his run on Twitter and was due to make a speech in his home state later in the day.

"I'm in. I'm running for president because Americans deserve a leader who will fight and win for them. - SW #Walker16," he wrote on Twitter.

Walker, 47, becomes the 15th major Republican to join the race. A 16th, Ohio Governor John Kasich, is expected to enter later this month.

Walker is currently polling in second place behind favorite Jeb Bush across a range of surveys, according to

Former secretary of state Hillary Clinton is the favorite to win the Democratic nomination in the race to succeed President Barack Obama.

Walker instituted a series of conservative reforms in Wisconsin, including major tax cuts, a right-to-work law that makes union dues voluntary instead of mandatory, a tightening of abortion laws and reining in of state regulations.

He was a virtual unknown nationwide until 2011, when his plan to reduce the collective bargaining power of state employees brought the wrath of unions, whose members led intense demonstrations in Wisconsin's capital city of Madison.