NEW YORK (CBSNewYork)Donald Trump is still leading the pack for the Republican presidential nomination, but a candidate once considered a long shot is gaining ground fast, according to a new poll.

Retired neurosurgeon Ben Carson has moved into second place in the CBS News/New York Times poll. Trump is in first with 27 percent.

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WEB EXTRA: See Complete Poll Results

Last month, Carson had just 6 percent in the survey of GOP primary voters nationally, which put him in a three-way tie for fifth place. While Trump’s lead has eroded in the past month from 11 percent to just 4 percent, he actually gained supporters — he was polling at 24 percent in August.

That signals that other GOP candidates are fading, most notably former Florida Gov. Jeb Bush and Wisconsin Gov. Scott Walker.

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Bush was in second place at 13 percent last month. He now has 6 percent support, which puts him in a three-way tie for third with former Arkansas Gov. Mike Huckabee and Florida Sen. Marco Rubio.

Walker, meanwhile, has plummeted from 10 percent in August, which put him in third place, to just 2 percent, or 10th place.

New Jersey Gov. Chris Christie‘s campaign is headed in the wrong direction as it tries to gain traction, according to the poll. His support has fallen from 3 percent last month to 1 percent, putting him in 12th place.

Former New York Gov. George Pataki is polling at less than 0.5 percent — down from 1 percent a month ago.

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The poll’s margin of error is 6 percentage points.