Poll: Trump leads Iowa, N.H.; Carson, Kasich move up

Another poll shows Donald Trump leading Republican races in Iowa and New Hampshire, with Ben Carson and John Kasich moving up and Jeb Bush falling back.

Trump currently leads Iowa with 29% support, followed by Carson at 22%, according to the NBC News/Marist Poll -- the only two candidates in double digits in the state where caucuses start the 2016 GOP nomination race.

Jeb Bush is third in Iowa with 6%, followed by Carly Fiorina, Rand Paul and Scott Walker each at 5%. Another trio -- Ted Cruz, Marco Rubio and Bobby Jindal -- are at 4% in Iowa, says the NBC News/Marist survey.

Walker, the governor of Wisconsin, led the same poll in Iowa back in July.

Trump, the businessman who has surged to the top of the Republican nomination race at this point, has a bigger lead in New Hampshire, site of the campaign's first primary, according to NBC News and Marist.

The billionaire is at 28% in New Hampshire, followed by Kasich -- the governor of Ohio -- at 12%, the polls says. Carson, a retired neurosurgeon, is third in New Hampshire at 11%.

Bush, who has led previous polls in New Hampshire, is fourth in the current NBC News/Marist Poll at 8%. The former Florida governor is followed by Fiorina at 6%.

Both the Iowa and New Hampshire polls were conducted Aug. 26-Sept. 2. The Iowa poll surveyed 390 potential Republican caucus-goers with an error margin of 5 percentage points, and the New Hampshire poll survey 413 potential Republican primary voters with an error mating of 4.8 percentage points.