Republican presidential candidate Ted Cruz narrowly leads Donald Trump in a new NBC News/Wall Street Journal national poll of Republican voters — 28 percent to 26 percent. The results are a statistical dead heat since the difference is within the poll’s margin of error, and diverge sharply from other national polls showing Trump with a comfortable lead. However, as NBC News notes, this was the first major poll conducted completely after Saturday’s GOP debate in South Carolina where many thought Trump had his worst debate performance.

[Update]: However, an even newer Fox News Poll, just out, also taken after the South Carolina debate, shows Trump maintaining a sizable lead over Cruz: 17 points.

The previous NBC national poll, taken last month, had Trump leading Cruz by 13 points. In the Saturday debate Trump said President George W. Bush lied about weapons of mass destruction in Iraq, suggested that maybe Bush should have been impeached, admitted he thought Planned Parenthood should receive taxpayer funding and — in perhaps the evening’s most surreal moment — claimed that Jeb Bush had recently threatened to moon the country.

But did the debate really take a toll on Trump’s support, or is the new poll a mere anomaly or blip in what remains a commanding lead for the real estate billionaire?  Trump continues to lead comfortably in South Carolina polls ahead of this Saturday’s primary there, even in polls taken completely after Saturday’s debate. However, three of the most recent South Carolina polls together suggest his lead may have shrunk from the upper teens down to the lower teens.

Pollsters Bill McInturff and Peter Hart and the firm Hart Research Associates conducted the national poll for NBC. McInturff said the drop in Trump’s numbers could mean he’s “right on top of a shift in the campaign,” reports NBC News. “When you see a number this different, it means you might be right on top of a shift in the campaign,” he said.

“What you don’t know yet is if the change is going to take place or if it is a momentary ‘pause’ before the numbers snap back into place,” he added.

Another, partial explanation for Trump’s decline in the poll could be an increase in “very conservative” Republican voters in the polling sample, though that would account for only about three points in the swing, NBC News says.

Another bright spot for Cruz in the new poll’s numbers: Cruz also comes out on top in various theoretical three-way matchups with Trump and one other GOP presidential candidate, suggesting that Cruz may continue to do well as the field is winnowed down to fewer and fewer candidates. Whether the hypothetical third candidate is Rubio, Carson, Kasich or Bush, Cruz comes out on top according to this new poll, though the margin varies from a razor thin 2-point lead over Trump when Rubio is in the mix, to 7 points when Carson is the third candidate.

A final bright spot in the poll for both Cruzio and Rubio — in theoretical one-on-one matchups with Trump (that is, Trump vs. Cruz and Trump vs. Rubio) each of the U.S. senators beats Trump by 16 points.

The Fox News Poll, taken on Feb. 15, 16 and 17, shows Trump with 36 percent, Cruz with 19 percent, Rubio with 15 percent and Bush, Carson and Kasich clustered around 8-9 percent.