Buttigieg has doubled his support since Monmouth’s last poll in September, while Sanders has jumped 6 points. Warren’s fall has been sharpest: She is down 12 points from September, while Biden has also slipped by 6 points.

New Hampshire voters will go to the polls on Feb. 11, eight days after the Iowa caucuses. Patrick Murray, director of the Monmouth University Polling Institute, said the jumble at the top of the poll is a sign of potential volatility coming out of Iowa.

“The race remains fairly wide open,” said Murray. “To the extent that New Hampshire voters could take some cues from Iowa, it’s also worth keeping an eye on lower-polling candidates like Klobuchar if any of the leading contenders stumble in the earlier Iowa contest.”

Among self-identified liberal voters, Sanders (26 percent) and Warren (24 percent) lead Biden (16 percent) and Buttigieg (16 percent). But the race is flipped among voters who identify as moderate or conservative: Buttigieg (25 percent) and Biden (22 percent) are ahead of Sanders (10 percent) and Warren (7 percent).

Below the top five candidates, the poll also represents a major blow to those hoping to make next week's debate in Iowa.

The five candidates above 5 percent in the Monmouth poll — the level of support candidates have to hit in four polls approved by the DNC to participate in the debate — have all already qualified.

The bubble candidates who haven't qualified — Andrew Yang, Tom Steyer, Cory Booker and Tulsi Gabbard — all measured below that. Gabbard and Steyer came closest, with 4 percent.

The deadline to qualify is Friday night, so it's unlikely anyone else will make it.

The Monmouth University poll was conducted Jan. 3-7, surveying 697 registered voters, 404 of whom said they were likely to vote in the Democratic presidential primary. The margin of error is plus or minus 4.9 percentage points.

Zach Montellaro contributed to this report.