US Senator Bernie Sanders of Vermont remains the clear front-runner in the New Hampshire Democratic primary less than three weeks away, according to a Suffolk University Political Research Center poll released Friday.

Sanders leads former US secretary of state Hillary Clinton, 50 to 41 percent, in the survey of likely Democratic primary voters.

After weeks of trading leads in polls this past fall, Sanders has pulled ahead in the most recent surveys of the Iowa caucuses and the New Hampshire primary, threatening Clinton’s onetime lock on the nomination.

The Suffolk poll also showed likely New Hampshire Democratic primary voters view Sanders favorably and as the most trustworthy candidate in the race. But they are wary of Sanders’s ability to win the general election and his stance on gun control.

“Everybody has been talking about the divide in the Republican party for months, but there is a real struggle also going on within the Democratic Party,’’ said Suffolk University pollster David Paleologos.

“New Hampshire Democrats are grappling with a number of issues, but for now Sanders is the clear choice,’’ Paleologos said.

Geographically, Sanders is bolstered by independent voters and clusters of support along the state’s border with Vermont. In New Hampshire, independent voters — nearly one-third of the state’s electorate — can request either party’s ballot in the primary.

The Suffolk survey calculated roughly one-third of the voters taking in the Democratic primary would be independent voters. Among them, 60 percent said they would back Sanders compared with just 24 percent who said they would back Clinton.

Some independent voters said that in addition to Sanders, they were also considering voting in the Republican primary for either Ohio Governor John Kasich or New York businessman Donald Trump. Asked which Republican candidate could make them vote in the GOP primary instead, 7 percent of respondents said Kasich and 6 percent said Trump.

“Independent voters are the really interesting group to watch,’’ Paleologos said. “If there is the perception that either the Republican or Democratic contest will be a blowout, they will flock to the other party’s primary.’’

Three out of four independents who said they plan to vote in the Democratic primary said none of the Republican candidates held any interest for them. That said, 20 percent of these Democratic voters said they do agree with some of the things Trump has said.

Clinton scored well among Democrats on two issues: Gun control and electability.

By a 44 percent to 30 percent gap, those surveyed said Clinton more closely reflected their opinion on gun control than Sanders. In the past, Sanders has backed legislation that gave immunity to gun manufacturers in gun-related deaths.

What’s more, 60 percent said that Clinton was better able to defeat a Republican in the general election. Just 27 percent felt Sanders was better positioned as the nominee to win the White House.

One area where Democrats were split was on the future of health care. Clinton supports tweaking the Affordable Care Act, President Obama’s signature health care overhaul law. Sanders has proposed a single-payer health care program that drastically cuts the role of private insurance companies.

A vast majority of respondents agreed Vice President Joe Biden should not enter the race. Only 17 percent of those surveyed said they would like to see him run for president.

A third Democrat in the race, former Maryland governor Martin O’Malley, received 2 percent in the survey from Suffolk University, which partners with the Globe on other polls.

The poll, which gave Sanders a 9-point lead over Clinton, came after a CNN/WMUR-TV poll earlier in the week said Sanders had a whopping 27-point advantage in New Hampshire. Clinton’s pollster dismissed the CNN/WMUR survey as an outlier. The Sanders campaign also said its research didn’t show that large of a lead.

The Real Clear Politics polling average, which takes into account every recent survey of the New Hampshire Democratic primary, shows Sanders with a 12.5-point lead over Clinton.

The Suffolk poll was conducted Jan. 19 to 21, making it the first survey to take place entirely after the last Democratic debate on Sunday.

The survey polled 500 New Hampshire voters who said they were “very likely’’ to vote in the state’s Feb. 9 Democratic primary. The poll has a margin of error of plus or minus 4.4 percentage points.

James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell or subscribe to his daily e-mail update on the 2016 campaign at www.bostonglobe.com/groundgame.