Ben Carson Erases Donald Trump's National Lead In New Poll

— -- Monday it was Iowa. Now it's nationwide.

Just a day after Ben Carson blew open a double-digit lead over Donald Trump in the state of Iowa in a new Monmouth University poll, a new poll shows the New York real estate mogul's national advantage is slipping away.

A new survey from CBS News-New York Times released this morning shows Carson narrowly leading with 26 percent support and Trump with 22 percent support, though it is within the nationwide telephone poll’s margin of sampling error.

Trump has not trailed in national polls for more than three months, surging to the front of the pack shortly after he entered the race. But now, Trump has slipped slightly, down 5 points in the past two weeks, while the retired neurosurgeon has ticked up 5 points in the same time frame, according to the CBS News-New York Times survey.

Florida Sen. Marco Rubio garnered 8 percent support in the new poll, with Jeb Bush and Carly Fiorina at 7 percent each.

Like in Iowa, Carson has opened up a wide lead among evangelicals, according to CBS. He leads Trump among that group by more than 20 points.

But Carson's support is softer than Trump's backers, according to the New York Times. Roughly four in five Carson supporters said they could still change their minds about whom to support, while more than half of Trump supporters said they had made their final decision.

Other polls have shown Trump's being overtaken by Carson in Iowa. Three consecutive Iowa polls have put Ben Carson on top, stretching his lead as wide at 14 points.

The climbing support for Carson comes despite his taking a break from public campaign events to go on a book tour amid controversial comments about gun violence and the Holocaust.