Donald Trump's lead over Sen. Ted Cruz in Saturday's South Carolina GOP primary has shrunk and is now just barely outside the margin of error. | AP Photo Cruz rises against Trump in South Carolina poll

Ted Cruz has made a deep cut into Donald Trump’s advantage in South Carolina, according to a new poll released on Friday.

The survey of likely Republican primary voters, conducted by Marist for NBC News and The Wall Street Journal, suggests a sudden tightening GOP race only a day before Saturday’s potentially pivotal contest — and after weeks when it seemed Trump would romp in the first-in-the-South primary.


While Trump leads Cruz 28 percent to 23 percent, his edge is barely outside the margin of error, in stark contrast to polls released in recent days that showed him with a clear double-digit advantage over the Texas senator. In the previous NBC/WSJ/Marist poll, conducted in mid-January, Trump held a 16-point lead over Cruz.

Marco Rubio finished third with 15 percent in the new poll, statistically tied with Jeb Bush, who picked up 13 percent. Ohio Gov. John Kasich and Ben Carson rounded out the field with 9 percent each, though barely statistically behind Bush.

Trump holds a clear advantage among those who said they have never voted in a South Carolina Republican primary, with 35 percent of that group backing him. The second-highest share of first-timers backs Cruz, at 18 percent, while 16 percent said they back Bush. The Manhattan businessman also leads among those 45 and older, unmarried voters and voters who do not practice a religion. He also holds a 2-percentage-point advantage over Cruz among those who said they do practice a religion, as well as among both veterans and nonveterans.

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Trump has not taken kindly to polls showing him in any place other than first or otherwise losing ground. On Thursday, Trump laced into The Wall Street Journal in particular, one of the sponsors of a national survey that showed Cruz up by a mere 2 points.

“In my opinion, it was a fix, you want to know the truth," he told Sirius XM’s Breitbart News Daily. “CBS just came out with a poll that says the same as every other poll. You know, Wall Street Journal came out with a poll, ’cause I’m not a big fan of The Wall Street Journal."

Six in 10 likely voters said they are strongly supporting a candidate at this point, with that share even higher among backers of Trump (71 percent) and Cruz (66 percent). Overall, 25 percent said they have a candidate they support somewhat, while 13 percent said they might vote differently on primary day.

But despite the new support for Cruz, there is at least one reason to proceed with caution. Among those who said they might ultimately vote differently than they indicated in the survey, Cruz is at the top, with 26 percent of his backers, followed by 22 percent of Bush supporters. Just 8 percent of Trump supporters said they might vote differently come Saturday.

Little has changed overall in the Democratic race, with Hillary Clinton picking up the support of 60 percent of likely primary voters. Bernie Sanders trails the former secretary of state, at 32 percent. In the previous NBC/WSJ/Marist survey, Clinton held a 37-point advantage over Sanders, at 64 percent to 27 percent.

The issue of race relations has loomed over the Democratic primary in South Carolina, a state with a historically important African-American electorate.

Among white voters, however, Sanders now holds a 5-point advantage after trailing Clinton by 11 points in January. The 16-point swing in his favor also comes with more modest gains among likely African-American primary voters.

In this survey, 68 percent of African-Americans said they would be supporting Clinton, down 6 points from January; 21 percent in that group said they would support Sanders, up 4 points during the same time period. Clinton’s advantage among African-Americans under the age of 45 is more narrow, at 52 percent to 35 percent. She leads 78 percent to 12 percent among African-Americans older than 45.

Marist College conducted the telephone poll Feb. 15-17, surveying 722 likely Republican primary voters with a margin of error of plus or minus 3.6 percentage points, and 425 likely Democratic primary voters with a margin of error of plus or minus 4.8 percentage points.