Donald Trump and Ben Carson are neck and neck in the key early voting state of South Carolina, according to a Monmouth University poll released Monday.

The poll found 28 percent of likely GOP primary voters said they would back Carson while 27 percent said they would support Trump in the primary scheduled in February.

Eleven percent of likely primary voters said they would support Sen. Marco Rubio, Florida, 9 percent would back Sen. Ted Cruz, Texas, and 7 percent would support former Florida Gov. Jeb Bush.

A recent CBS News Battleground Tracker poll found Trump led Carson in South Carolina 40 percent to 23 percent.

None of the other 10 candidates, however, scored higher than 2 percent in the Monmouth University poll.

Since Monmouth's last poll in South Carolina from August, Carson has nearly doubled his support while Trump's support has remained relatively stable. Rubio's support has increased by 5 percentage points and support for Cruz has gone up by 4 percentage points. Meanwhile, Bush's support has dropped by 2 percentage points.

Seventeen percent of likely primary voters said they are completed decided on which candidate to vote for while 39 percent said they have a strong preference but could consider others. Twenty percent said they're completely undecided.

In a hypothetical contest that excludes Trump, Carson, Cruz and Carly Fiorina, Rubio leads the GOP pack with 32 percent support.

The survey also found Carson has improved his support across the ideological spectrum since August. He also leads Trump 33 percent to 24 percent among evangelical Christians and leads the field among voters under the age of 50 38 percent to 24 percent compared to Trump.

More than three-quarters gave Carson a favorable rating and 12 percent viewed him unfavorably. Sixty-two percent gave Rubio a favorable rating and 18 percent said they viewed him unfavorably. Fifty-eight percent gave Trump a favorable rating and 29 percent said they viewed him unfavorably.

The survey polled 401 South Carolina voters likely to vote in the GOP primary from November 5 to November 8 with a 4.9 percentage point margin of error.