Former Vice President Joe Biden and Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts are atop the first poll following last week’s Democratic presidential nomination debates.

Biden stood at 21% among likely Democratic primary voters in New Hampshire, according to a Suffolk University survey for the Boston Globe released Tuesday, with Sanders at 17% and Warren at 14%. Sen. Kamala Harris of California registered at 8%, with South Bend, Ind., Mayor Pete Buttigieg at 6%.

According to the new poll, Rep. Tulsi Gabbard of Hawaii was at 3% and Sen. Michael Bennet of Colorado was at 2%.

Sens. Cory Booker of New Jersey, Kirsten Gillibrand of New York and Amy Klobuchar of Minnesota stood at 1% in the survey, as did former representative John Delaney of Maryland, entrepreneur Andrew Yang and billionaire progressive and environmental advocate Tom Steyer. Everybody else in the record-setting field of two-dozen Democratic White House contenders registered less than 1%.

The poll’s sampling error among likely Democratic primary voters was plus or minus 4.4 percentage points. And with six months to go until New Hampshire’s primary, the race remains extremely competitive.

But Suffolk University Political Research Center director David Paleologos emphasized that Biden – as well as Sanders and Warren, who hail from two of the Granite State’s neighbors – will be difficult to knock out of the top tier because a significant percentage of their backers say they’ve already made up their minds on whom they’ll support in the primary.

According to the survey, 48% of Sanders supporters and 45% of Biden supporters say they would definitely vote for the candidate they’re currently backing. That percentage stands at 35% for Warren, 34% for Buttigieg and 20% for Harris.

Paleologos highlighted that Biden should remain in the top tier “because he’s crushing opponents among older voters, 2016 Hillary Clinton primary voters, and union households. He owns those categories.”

He added that Sanders is “retaining a good portion of his 2016 primary vote and he’s a known quantity” and that Warren should also remain in the top tier “because the progressives not with Sanders have found a new face and someone they found equally or more comfortable supporting.”

The pollster also pointed to Warren as having the best ability to grow her support as some of the lower-tier contenders likely drop out of the race in the coming months. The poll suggested that 21% said they’d back her after their first choice. That’s far ahead of Biden and Sanders, who each were at 13% as the second choice of voters, with Harris at 9% and Buttigieg at 8%.

The release of the poll comes as many of the longer-shots for the nomination scramble to qualify for the third round of debates, which will be held in early September in Houston. Nearly two-thirds of those questioned said that if a candidate doesn’t make the debate stage in September, they should drop out of the race.

The live telephone operator survey of 500 likely Democratic primary voters in New Hampshire was conducted Thursday through Sunday.