Ben Carson is starting to tumble ...
A Fox News poll of Republican voters released on Sunday found Carson tumbling 6 points, dropping back down to 18% support.
In the poll, he trailed front-runner Donald Trump, who has held steady, by 10 points. Fox's poll also put Sens. Ted Cruz (R-Texas) and Marco Rubio (R-Florida) in a tie for third with 14% each.
Carson also has slumped in Iowa, the crucial first-nominating state where Carson has gained traction with the state's more conservative and evangelical groups.
According to a CBS poll released Sunday, Carson's support in the Hawkeye State has dipped to 19%. That put him below Trump, whose support sits at 28% in the poll, and Cruz, who garnered 21%. For Carson, it's a quick turn of events from last month, when he regularly surged ahead of Trump in Iowa polls.
And in the first-in-the-nation primary state of New Hampshire, Carson slipped to third in polls conducted by CBS and Suffolk University.
Carson's best standing Sunday came in a Washington Post/ABC poll. That survey showed Trump maintaining his healthy lead over the field, with 32% of likely Republican voters preferring the real-estate tycoon. Carson also held steady at 22% support, exactly the same as where he stood one month ago in the survey.
Some polling analysts - many of whom caution that early polls are volatile and not predictive of eventual election outcomes - have been skeptical of Carson's rise.
Princeton University professor and polling expert Sam Wang told Business Insider late last month that the fact that many of Carson's supporters were not fully committed to voting for him suggested that Trump's support may be more solid than Carson's.
"That softness of support for Carson might put him in a similar category as Michele Bachmann, Newt Gingrich, and Rick Santorum, all of whom rose to similar levels of support for several months, but then lost that support by the time voting started," Wang said. "Carson's rise has not yet lasted longer than they did."
"The hardening of support for Trump is extremely interesting and suggests that he might have staying power. His numbers have also lasted longer than those transient candidates from 2012. That puts him in a category more like Pat Buchanan in 1992 and 1996, who didn't get the nomination, but was a major force within the Republican Party."