In the Republican primary race, the newest NBC News/SurveyMonkey online poll shows Donald Trump has the frontrunner spot to himself, with 28% support among Republican and independent voters who lean Republican. Support for Ben Carson, who was tied with Trump in last month’s online poll, has fallen off by 8 points and the former neurosurgeon is now tied with Ted Cruz at 18%. Trailing not too far behind is Marco Rubio, at 11%. The next tier of candidates has a lot of catching up to do, with Jeb Bush at 4% and Chris Christie and Carly Fiorina each with 3%.

PHOTOS - On the Stump: Donald Trump's Presidential Campaign

During the volatile primary season, the attention that is gained from being the lead candidate in the polls can be a mixed blessing. The media tends to shift its focus to those candidates leading the race – and that spotlight can seem especially harsh to those who are newer to the political scene. At the same time, rival candidates are quick to target any apparent or imagined flaw of those in the lead. This is what happened to Ben Carson during the last two weeks, as he came under scrutiny for biographical details in his memoir and criticism for his lack of foreign policy expertise.

Carson and the other Republican candidates still have more than two months before the Iowa caucus and New Hampshire primary to gain traction. Looking at a number of subgroups may offer some clues as to how the early contests could go. The NBC News/SurveyMonkey poll was conducted nationwide of 5,775 adults, including 2,440 Republican and Republican-leaning voters, which allows for us to look at key voting blocs.

PHOTOS - On the Stump: Ben Carson's Presidential Campaign

Ben Carson is still the preferred candidate of 25% of white evangelicals, but Donald Trump (23%) and Ted Cruz (22%) have clearly eaten away at what used to be the main pillar of Carson support. Among those who identify as very conservative, Ted Cruz now has the highest level of support, with 40%, overtaking both Carson (15%) and Trump (28%).

Carson has also seen his backing erode among both men and women, and their vote preferences are now being diverted to other candidates.

Among those with college degrees or more, the Republican race is utterly divided, with Trump, Carson, Cruz and Rubio getting nearly equal levels of support. Trump has regained his lead among leaned Republican voters with high school degrees or less. And Ted Cruz has made gains among all these groups in the last month.

PHOTOS - On the Stump: Ted Cruz's Presidential Campaign

Stephanie Psyllos, Hannah Hartig, and Josh Clinton contributed reporting.

The NBC News/SurveyMonkey online poll was conducted from November 15-17, 2015 among a national sample of 5,755 adults aged 18 and over and including a sample of 2,440 Republican voters and independent voters who lean Republican. Respondents for this non-probability survey were selected from the nearly three million people who take surveys on the SurveyMonkey platform each day. Overall results have an error estimate of plus or minus 1.9 percentage points and the error estimate for the leaned Republican voters is plus or minus 2.9 percentage points. A full description of our methodology and the poll can be found here.

The poll was produced by the Data Analytics Lab of NBC News in conjunction with Penn’s Program on Opinion Research and Election Studies with data collection and tabulation conducted by SurveyMonkey.