Former Vice President Joe Biden and Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts remain the top three contenders in the first poll conducted in the first-in-the-nation presidential primary state of New Hampshire following last week’s Democratic nomination debates.

But the Suffolk University survey for the Boston Globe released Tuesday also indicates a slip in support for Sen. Kamala Harris of California when compared with polls conducted prior to the debates.

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Biden stands at 21 percent among likely Democratic primary voters in New Hampshire according to the survey, with Sanders at 17 percent, Warren at 14 percent, and Harris at 8 percent.

Biden stood at 23 percent in an average of the two live operator surveys – University of New Hampshire/CNN and Saint Anselm College – conducted in early to mid-July, before the debates. Warren averaged 18 percent, Sanders 15 percent and Harris 14 percent.

South Bend, Indiana Mayor Pete Buttigieg registers at 6 percent in the new poll, with Rep. Tulsi Gabbard of Hawaii at 3 percent and Sen. Michael Bennet of Colorado at 2 percent.

Sens. Cory Booker of New Jersey, Kirsten Gillibrand of New York and Amy Klobuchar of Minnesota stand at 1 percent in the survey, as do former Rep. 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 percent.

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The poll’s sampling error among likely Democratic primary voters was plus or minus 4.4 percentage points. And with six months still 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 states that neighbor New Hampshire – will be difficult to topple from 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 percent of Sanders supporters and 45 percent of Biden supporters say they would definitely vote for the candidate they’re currently backing. That percentage stands at 35 percent for Warren, 34 percent for Buttigieg and 20 percent 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.”

Paleologos also said Warren may have 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 percent of respondents said they’d back her after their first choice. That’s far ahead of Biden and Sanders, who each were at 13 percent as the second choice of voters, with Harris at 9 percent and Buttigieg at 8 percent.

Sixty percent of those questioned in the survey said they’re open to changing their mind.

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.