AUGUSTA — A new poll shows oyster farmer Graham Platner leading Gov. Janet Mills by a significant margin in the Democratic primary for the U.S. Senate.

The Emerson College poll shows Platner at 55% to Mills at 28%. That leaves 13% undecided and 4% choosing someone else.

The poll of 530 likely Democratic primary voters has a margin of error of 4.2%.

“Graham Platner has a significant lead over Gov. Mills, which is outside the poll’s margin of error,” Spencer Kimball, executive director of Emerson College Polling, said in a statement. 

Kimball also noted male voters support Platner by a 41-point margin and he’s leading among women by 18 points.

The poll was taken March 21-23, five days after Mills began running the first of a series of ads highlighting Platner’s past comments about rape.

Today, Mills released a new ad featuring a female Army veteran and military sexual assault survivor who says in the ad: “for all women who have ever been raped, the pain never goes away.”

The ad quoted Platner writing on social media that if women want to avoid rape they should make sure they don’t get so altered that “they wind up having sex with someone they don’t mean to. 

Platner responded last week in Augusta.

“When I read through my old internet posts when they resurfaced six months ago, I was horrified,” he said. “I did not recognize in them myself or the man that I am today.”

He said 13 years ago he “posted awful things” as he struggled to find meaning in his life. Previously, Platner has said he suffered post-traumatic stress disorder and depression after serving in Iraq and Afghanistan.

“I am sorry, but it does not reflect in any way who I am today or the beliefs I hold,” he said. 

The Emerson poll also gauged how Platner and Mills would do in a hypothetical matchup with Sen. Susan Collins, the Republican they are both hoping to defeat in November.

The poll showed Platner at 48% and Collins at 41% with 12% undecided. It showed Mills at 46%, Collins at 43% with 11% undecided.

“In the general election, Mills and Platner both have an edge over incumbent Sen. Collins among women voters: Platner leads 52% to 35%, and Mills leads 53% to 36%,” Kimball said.

Voters in the June 9 Democratic primary will have three choices: Platner, Mills and David Costello of Brunswick, who spent 30 years working as a senior level government official.