Sen. Ted Cruz has erased Donald Trump’s lead in a new national poll that could signal a significant shift in the race for the Republican nomination with primary election season in full swing.

According to a NBC News/Wall Street Journal poll released Wednesday, 28 percent of Republican primary voters support Cruz, while 26 percent back Trump. The poll had a margin of error of plus or minus 5 percentage points, leaving the candidates in a virtual tie.

Trump was leading by 13 points in the same poll in January. He has consistently topped national surveys of Republicans for months, as he has dominated news media coverage and batted away opponents who started to gain on him. Ben Carson, the retired neurosurgeon, briefly displaced Trump in a New York Times/CBS poll in October and in a Public Religion Research Institute poll the following month.

It remains unclear whether the NBC/WSJ poll was an outlier or a harbinger. Two other polls released Wednesday — from Quinnipiac University and USA Today/Suffolk University — showed Trump with commanding leads nationally over Cruz and the rest of the field.

Bill McInturff, the pollster who conducted the NBC/WSJ survey, said in a statement, “When you see a number this different, it means you might be right on top of a shift in the campaign.”

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

The poll was conducted after the New Hampshire primary on Feb. 9 and the Republican presidential debate Saturday — a contentious affair during which Trump was attacked from all sides and came off as angry and unsteady at times. Some political analysts suggested that he might have damaged his standing with Republicans by loudly criticizing former President George W. Bush for failing to keep Americans safe on Sept. 11, 2001, and for bungling the Iraq war.

The NBC/WSJ poll noted that its sample of 400 Republican primary voters consisted of more people who consider themselves “very conservative” than its January poll. This likely gave Cruz a boost of about 3 percentage points.

Trailing Cruz and Trump were Sen. Marco Rubio with 17 percent, Gov. John Kasich of Ohio with 11 percent and Carson with 10 percent. In last place was Jeb Bush, with the support of just 4 percent of Republican voters.

While the latest national numbers might be worrying for Trump, things are looking up in South Carolina ahead of the Republican primary there on Saturday.

A Monmouth University survey of likely Republican voters released Wednesday found that 35 percent planned to back Trump. Lagging far behind were Cruz and Rubio, with 19 percent and 17 percent, respectively. Kasich, Bush, and Carson were all stuck in single digits. The poll had a margin of error of plus or minus 5 percentage points.

“The overwhelmingly negative feelings of South Carolina Republicans toward the political establishment have helped Trump build upon the support he enjoyed since the summer,” Patrick Murray, director of the Monmouth University Polling Institute, said. “The fact that six candidates are still in the race partly accounts for the size of his lead, despite the fact that he has relatively high negative ratings overall.”