US conservatives gathering at their annual conference have chosen Republican Senator Rand Paul as their top pick to run for president in 2016.
It is the second successive year that the libertarian-leaning Paul, son of former congressman and presidential candidate Ron Paul, won the straw poll at the Conservative Action Political Conference, or Cpac.
Paul topped a field of 23 candidates with 31 per cent of the vote, easily defeating firebrand "tea party"-backed Senator Ted Cruz, who finished second with 11 per cent.
Ben Carson, a neurosurgeon who has emerged as a powerful conservative voice in recent years, finished third, while Chris Christie, the New Jersey governor burdened with a political scandal, came in fourth.
"I am grateful for all the attendees who stood with me," Paul said, referring to the "Stand with Rand" movement that sprouted a year ago after he gave a 13-hour speech on the Senate floor to oppose President Barack Obama's use of drones to target extremists.
"The fight for liberty continues," Paul said.
The vote is watched closely, not necessarily as a prediction of who will emerge as the Republican candidate, but as a barometer of how core conservatives see those who might make the ballot.
Nearly 2,500 Cpac attendees participated in the vote, which featured questions on issues including the legalisation of marijuana use.In all, 41 per cent said it should, according to Republican pollster Tony Fabrizio, who organised the straw poll.
Fabrizio said issues that drove many at the conference included the need to protect individual freedoms, shrink the size and scope of government, and prevent government's intrusion into people's lives.