Wisconsin Governor Scott Walker has announced he is seeking the Republican nomination for US president.
The 47-year-old tweeted “I’m in”, joining a field of 14 others in his party competing for the 2016 election.
“I’m running for president to fight and win for the American people,” he said in a video released on Monday.
He will formally announce his run for US president later at an event in Milwaukee.
The governor defeated a recall election and clashed with labour unions in his home state, and cut taxes by nearly $2bn (£1.3bn).
In addition to siding with business groups in Wisconsin, he has also legalised carrying concealed weapons, introduced further restrictions on abortions and made photo identification a requirement to vote.
Analysis: Anthony Zurcher, BBC News
Scott Walker enters the race for the Republican presidential nomination in an enviable position. For most of this year he’s been the frontrunner in Iowa, which is the first state to vote in 2016. He’s also among the leaders in New Hampshire, making him the only Republican candidate with a realistic chance of starting the primary season with back-to-back wins.
Mr Walker’s appeal has been as a candidate who energises grass-roots conservative Tea Party activists while, as an incumbent governor of a moderate state, is still acceptable to the party’s establishment.
The challenge for the Wisconsinite will be to continue to bridge that gap as the ideological components of his party are courted with more focused appeals by his competitors. If he can post strong results in solidly conservative Iowa and independent-minded New Hampshire, he’ll have demonstrated that he can achieve such a feat – and could be well on his way to the nomination.
2016 runners and riders
- The early Republican frontrunner is Jeb Bush
- Hillary Clinton will have learnt much from her failed campaign of 2008
- Florida senator Marco Rubio lost some right-wing fans by backing a bipartisan immigration reform package
- Wisconsin governor Scott Walker appeals to both the Republican establishment and the Tea Party
- Libertarian Rand Paul has his supporters – and enemies – among Republicans
- Veteran congressman Bernie Sanders is running as a Democrat despite never formally being part of the party