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Donald Trump is still clinging to first place nationally after his second-place finish in the Iowa caucuses Monday, but his lead has diminished significantly. The first post-Iowa national poll out Thursday by Democratic firm Public Policy Polling reveals that Trump dropped 9 points from the last poll released mid-December, from 34 percent to 25 percent.

While Iowa hurt Trump's numbers, it's having the exact opposite effect on Florida Sen. Marco Rubio's chances. The third-place finisher in the Iowa caucuses climbed 8 points from the last poll to tie with Texas Sen. Ted Cruz for second place nationally, with 21 percent support each. That 4-point margin marks a significantly narrower lead for Trump than he had in December, when he led Cruz by 16 points and Rubio by 21 points.

Retired neurosurgeon Ben Carson came in fourth with 11 percent support. No other candidates got more than 5 percent.