Both candidates are scheduled to visit Massachusetts Monday — a signal of the state’s importance in the nominating contest and an anticipated close outcome. Clinton is throwing rallies in Springfield and Boston, and Sanders is headlining an evening event in Milton.

Clinton draws 50 percent of the vote, while Sanders picks up 42 percent and eight percent remain undecided, according to the Suffolk University poll released Sunday. The poll was conducted Thursday, Friday, and Saturday.

Former secretary of state Hillary Clinton holds an eight-point lead over Bernie Sanders in a new poll of Massachusetts Democratic primary voters, suggesting that the Vermont senator needs to attract significant support during the final push to eke out a much-needed win in Tuesday’s Massachusetts presidential primary.


Tuesday’s primary vote in Massachusetts is one of a dozen Super Tuesday contests around the country.

Clinton has shown strength in recent days with a landslide win in South Carolina’s primary. Massachusetts is viewed as a vital test of Clinton’s durability as the party favorite, and her success here could prove a major blow to Sanders’ hopes for an upset.

But it is Sanders who has attracted more voters in recent months, as doubts about Clinton have persisted.

“She’s not growing at all,” said David Paleologos, director of the Suffolk University Political Research Center, referring to Clinton’s relatively static showing in primary polling. “Sanders is growing, but he’s not catching her. He hasn’t closed the deal. If she beats him here, if the lead holds up, I think this is one of those states he was counting on to win. It still could happen, but it’s going to be a challenge.”

Paleologos called the primary a “tough-to-poll race” because unenrolled voters can vote in either the Democratic or Republican contest. Among registered Democrats, Clinton enjoys a solid 22-point advantage. Sanders has a 17-point lead among unenrolled voters.


“It really depends on a decision that independent voters are going to make on Monday night,” he said. “People could jump out of the Republican primary and say ‘I’m going to send a message to Hillary Clinton and vote for Bernie.’ ”

The state’s Democratic establishment also has a lot on the line Tuesday, having almost universally lined up behind Clinton. The party’s left-leaning activists have largely sided with Sanders, who, like GOP front-runner Donald Trump, has also attracted independent and more irregular voters.

The Suffolk poll roughly echoes a WBUR Democratic primary survey released last week showing Clinton with a lead of five percentage points over Sanders.

Roughly half of those Democrats polled think Clinton will win the White House, while just 12 percent expect Sanders to, and 16 percent think Trump will.

Despite Democratic support for Clinton, Sanders remains well-liked overall among Democrats: Seventy-one percent viewed him favorably, compared with 67 percent for Clinton.

On the Republican side, unenrolled voters likely to vote in the Democratic primary see Trump in a harshly negative light: More than three-quarters said they hold unfavorable opinions of him. In fact, the only GOP contender to receive a favorable rating is Ohio Governor John Kasich, who enjoys approval from two-thirds of likely Democratic primary voters.

That fondness could shape results for the Clinton-Sanders match-up, as independents decide in which primary they want to vote Tuesday.

In November, Suffolk tested Democrats’ views on the race and found that Clinton held a commanding, 25-point lead. Sanders has gained ground largely thanks to undecided voters leery of the former senator and first lady but do not yet appear to be sufficient to catch the longtime front-runner.


“He’s made up a lot of ground and Clinton hasn’t grown since November,” Paleologos said.

Massachusetts has long been a Clinton family stronghold. In 2008, the state served as a bright spot for Hillary Clinton when she won the primary here despite several of the state’s top Democrats backing then-Senator Barack Obama.

Much of Sanders’ support stems from voters who were not yet old enough to participate in that 2008 race. Among voters aged 18 to 45, he leads, 50 percent to 42 percent. But among the younger subset of 18-to-35-year-olds, his lead is 17 points. Voters in the older subset of that group are split evenly, according to the poll, rendering them a key bloc Tuesday night.

Clinton continues to face a gender gap, winning easily among women with 55 percent of the vote but trailing Sanders among men by eight points. Paleologos said women will probably account for between 56 percent and 60 percent of Tuesday’s primary electorate.

The only region of the state where Sanders leads is Worcester and the western counties. Clinton beats him everywhere else, most dominantly in Suffolk County, where the poll puts her 18 points ahead.

White voters prefer Clinton by a narrow margin, but nonwhites break her way by 22 percentage points. She also leads among those without children, while Sanders holds a small edge among those with children.


Of the 21 percent of likely voters whose household includes a union member, Sanders holds a small edge.

Conducted Feb. 25 through Feb. 27 among 500 likely Democratic primary voters, the poll carries a margin of error of plus or minus 4.4 percentage points.

Jim O’Sullivan can be reached at jim.osullivan@globe.com. Follow him on Twitter at @JOSreports.