Trump has 24% support compared to Carson's 23% in a new Quinnipiac University survey.
Florida Sen. Marco Rubio comes in No. 3 with 14% support, and Texas Sen. Ted Cruz is No. 4 with 13%.
Former Florida Gov. Jeb Bush is next with just 4% support, followed by Carly Fiorina, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich at 3% each, and then Kentucky Sen. Rand Paul at 2%.
Among Democrats, Hillary Clinton has maintained her hefty lead -- with 53% backing to Vermont Sen. Bernie Sanders' 35%.
The worst news for Clinton comes in a head-to-head with Carson, where she trails 50% to 40%.
"Is there a doctor in the house? There certainly is and at the moment Dr. Ben Carson is delivering a troubling diagnosis to Secretary Hillary Clinton," said Tim Malloy, assistant director of the Quinnipiac University Poll, in a release accompanying the poll. "With the election one year away, Ben Carson has surgically cut away all but one GOP opponent and taken a scalpel to Hillary Clinton's lead."
The other head-to-heads are closer: Clinton trails Rubio, 46% to 41%, but tops Trump 46% to 43%, Cruz (46% to 43%) and Christie (46% to 41%). Sanders performs slightly worse in each GOP match-up.
Three candidates in the race have negative favorability ratings.
Bush is in by far the worst shape, with just 1-in-4 of those surveyed saying they have a positive view of the son and brother of former presidents while 58% hold a negative view. Trump is viewed favorably by 37% and unfavorably by 56%, while Clinton's ratings of 42% and 52% are also underwater.
The best margin goes to Carson (49% to 25%), followed by Rubio (39% to 25%) and Cruz (35% to 32%).
Sanders' favorability rating is 39% to an unfavorability rating of 36%.
The poll surveyed 1,144 registered voters nationwide between October 29 - November 2 with a margin of error of plus or minus 2.9 percentage points. The survey includes 502 Republicans, with a margin of error of plus or minus 4.4 percentage points, and 480 Democrats, with a margin of error of plus or minus 4.5 percentage points.