A new UMass Amherst/WCVB poll conducted by YouGov shows that a sharp divide has formed in this year's Democratic primary contests, with some races boasting a clear favorite and others too close to call as the September 6 primary approaches.

Attorney General Maura Healey leads by a wide margin in the race to become the Democratic nominee for governor over state Senator Sonia Chang-Díaz, who effectively ended her campaign in June but remains on the ballot. Healey is ahead 69-14 without leaners and 73-14 with leaners.

"The only certainty that I can take out of our results is that Maura Healey is going to be the Democratic nominee for governor," Tatishe Nteta, a political scientist at UMass Amherst and the director of the UMass Poll, said.

In contrast, the race for attorney general is a dead heat. Labor lawyer Shannon Liss-Riordan leads former Boston City Councilor Andrea Campbell, 26-25 without leaners and 29-28 with.

The survey was completed before the race's third candidate, former Mass. Assistant Attorney General Quentin Palfrey, dropped out and endorsed Campbell. His support was 10 percent without leaners and 11 percent with.

"Even though he came out in support of Campbell, it's unclear whether or not his supporters are going to follow that directive," said Nteta. "So this is going to make it a really interesting last few days of the campaign."

The ability of Campbell and Liss-Riordan to woo Palfrey's supporters may be limited by changes in voting habits. Just 37 percent of the poll's respondents said they plan to vote in person on September 6, compared to 47 percent who plan to vote by mail and 15 percent who plan to vote early and in person.

Among voters who said they won’t be voting in person, 42 percent said they had already cast their ballot.

The auditor's race is also too close to call. Chris Dempsey, a former state assistant secretary of transportation, and state Senator Diana DiZoglio are tied, with 22 percent backing without leaners and 26 percent with. Without the leaning option, 56 percent of poll respondents said they don't know who they will back.

In the race for secretary of state, seven-term incumbent Bill Galvin has a sizable lead over NAACP Boston head Tanisha Sullivan, 46-27 without leaners and 49-30 with. But 27 percent — 20, with leaners removed — say they remain unsure of their vote.

Salem Mayor Kim Driscoll is the frontrunner in the race for lieutenant governor. She was backed by 25 percent of the likely Democratic primary voters surveyed, compared to 15 percent for state Senator Eric Lesser and 13 percent for state Representative Tami Gouveia.

When respondents who said they didn’t have a preference were asked if they were leaning toward a particular candidate, Driscoll retained her lead, drawing 31 percent support compared to Lesser's 17 and Gouveia's 15.

Nteta noted that many voters are still undecided in the lieutenant governor contest. Forty-six percent of respondents initially said they still aren't sure who they'll support. That number drops to 37 percent with leaners included.

"Given the number of undecided voters, [Driscoll’s] lead, in my mind, is relatively tenuous," Nteta said. "Anything can happen in the waning days of a campaign.”

The poll also found strong support for efforts by Governor Charlie Baker, the state Legislature and Attorney General Maura Healey to protect the right to an abortion in Massachusetts. In each case, just four percent of the likely Democratic primary voters polled somewhat or strongly disapproved of each's performance in that area.

Respondents also had starkly different assessments of the direction of the state and the country, with 39 percent saying the U.S. is on the right track and 66 percent saying Massachusetts is.

The poll was conducted from August 26 to August 29, and has a margin of error of 5.1 percent. The full results are available here.