Washington - Hillary Clinton is the favourite among Democratic voters in the mid-western state of Iowa, where the next US presidential campaign will begin in 2016, according to a poll released on Wednesday.
But the survey "shows no favourites" among prospective Republican candidates, Suffolk University in Boston said in the poll.
With President Barack Obama's re-election little more than a year ago, the US political apparatus is already gearing up for the next round.
The Iowa caucuses in early January 2016 will kick off the state-by-state primary voting process in which the parties decide their candidate for the presidency. The mid-western state is a "must" stop for candidates in the six-month nominating process.
In the poll, 63% of Democratic voters preferred former first lady and secretary of state Clinton, 12% tipped for Senator Elizabeth Warren of Massachusetts and only 10% for Vice President Joe Biden.
None of them has declared a candidacy and Clinton has given sketchy answers when asked if she will run. Her supporters, however, have already started to organise.
On the Republican side, there was no clear front runner.
Republican voters indicated anywhere from 6% to 11% support distributed among 12 hopefuls.
Former Arkansas governor Mike Huckabee, who ran for the Republican nomination in 2008, led the pack with 11% and former Florida governor Jeb Bush, son of one president and brother of another, received 10%.