Leading Democratic presidential candidates Hillary Clinton, left, and Bernie Sanders.
Leading Democratic presidential candidates Hillary Clinton, left, and Bernie Sanders.

A new U.S. political survey shows support waning in the rural state of Iowa for Democratic presidential contender Hillary Clinton, five months ahead of the first presidential nominating contest.

In their latest survey of voter preferences in the state, the Des Moines Register and Bloomberg Politics reported Sunday that 37 percent of Democrats likely to participate in the February 1 nominating caucuses favor the former secretary of state. Independent socialist Bernie Sanders, who is campaigning against the influence of big corporations in American life, drew 30 percent in the survey, while 14 percent favored Vice President Joe Biden, who is weighing a late entry in the party's nominating contest.

It was the first time in four polls this year that Clinton's support fell below 50 percent. Other surveys have shown Clinton's support dropping nationally, with questions being raised about her use of a private email server while she served as the country's top diplomat, possibly leaving classified information exposed to security breaches.

Republican contest

In the Republican nominating contest, the Iowa polling showed two political novices with the most support, billionaire real estate mogul Donald Trump with 23 percent and former neurosurgeon Ben Carson with 18 percent. Established Republican politicians, most of them current or former governors or senators, all drew 8 percent or less support.

New Jersey Governor Chris Christie, one of 17 Repu
New Jersey Governor Chris Christie, one of 17 Republican presidential candidates, campaigns during a stop at a Greek festival in Manchester, N.H., Aug. 29, 2015.

Trump is dominating the Republican contest nationally with his call to deport about 11 million immigrants in the country illegally and to build an impenetrable wall along the country's southern border with Mexico to halt the flow of more immigrants into the United States.

Other Republican contenders have sought to curry favor with party voters with their own get-tough-on-immigration stances. New Jersey Governor Chris Christie said that 40 percent of those in the country illegally have overstayed legal visas, but ought to be monitored when they enter the country much the way packages are shipped in the country by cargo carriers.

"We need to have a system that tracks you from the moment you come in," Christie told political supporters in New Hampshire, "and then when your time is up, whether it's three months, or six months, or nine months or 12 months, however long your visa is, then we go get you and tap you on the shoulder and say, 'Excuse me. Thanks for coming. Time to go.'"

The Republican presidential candidates have focused their proposals on the U.S. border with Mexico. But one contender, Wisconsin Governor Scott Walker, said Sunday that another border wall -- along the 8,900-kilometer U.S.-Canadian border -- "is a legitimate issue for us to look at."