A young girl with desperate, teary eyes and a masculine hand covering her mouth. A woman holding a hand-lettered “HELP’’ sign behind what appears to be a shower door.

And the ominous text: “He is allowing boys to shower in girls locker rooms.’’

This was the blunt message conveyed in a direct-mail piece recently sent to voters in at least two suburban state House districts north of Boston — attacking Democrats’ support for one of the most controversial bills of the legislative session.

One targeted state Representative ­Michael Day. “Shame on you, Michael Day,’’ reads the mailer, sent by the Marlborough Republican City Committee.

The piece attacks Democrats’ votes in favor­ of a measure to protect transgender people from discrimination in public accommodations, including bathrooms. Opponents have raised the specter that the law, which allows transgender people to use the bathroom that matches the gender they identify with, will give men access to women’s locker rooms and bathrooms.

“No one supports discrimination,’’ the mailer states. “However, everyone wants common sense protections.’’

Paul Ferro, chairman of the Marlborough committee, confirmed Thursday that his group had sent the mailer to Day’s constituents, but declined to say which other districts had been targeted. Ferro said that information would appear in campaign finance documents filed after the election.

Representative Ken Gordon said the fliers also landed in his district, which covers Bedford, Burlington, and part of Wilmington. Gordon is facing GOP challenger Paul Girouard.

Day is defending a House seat that covers Stoneham and Winchester against Republican challenger Caroline Colarusso, who has been endorsed by GOP Governor Charlie Baker.

The anti-Day mailer highlights an enduring schism within the state Republican Party, between social conservatives still dissatisfied with Baker and a more moderate strain of the GOP.

Baker signed the bill in question into law, with little fanfare, over the summer.

Further complicating matters is that Baker, during his unsuccessful 2010 challenge to Democratic governor Deval Patrick, campaigned against similar legislation, derisively calling it the “bathroom bill’’ and promising to veto it if he were elected and it came to his desk.

A Baker political spokesman said Thursday that the governor was “pleased to sign’’ the measure.

“He does not condone this campaign tactic,’’ said the spokesman, James Conroy.

The Marlborough group has become something of a haven for the state party’s right wing, operating independently of the state GOP apparatus in support of more conservative candidates.

Day began using the piece as a fund-raising mechanism, ripping “this outrageous and abhorrent mail’’ and asking supporters for donations in an e-mail sent Wednesday from his campaign account.

In an e-mailed statement, Ferro said, “We expect that the outrage is that Michael Day’s true voting record has been exposed. He should be apologizing to parents for ignoring public safety measures.’’

Day fired back, saying he expected his constituents to reject the piece “uncategorically.’’

“I would guess it’s created and approved by some pretty disturbed individuals,’’ Day said in a phone interview, adding, “I really do think this is on the Mass. Republican Party.’’

Colarusso said voters should be alarmed by Day’s votes, which included opposition to amendments that garnered some Democratic support.

“As a mother, I’m appalled,’’ Colarusso said. “My opponent didn’t vote for any – none – of the public safety measures in the bathroom bill.’’

“Level 2 and 3 sex offenders, they shouldn’t be allowed to falsely claim transgender status just to enter a ladies room or a locker room,’’ Colarusso said. “Listen, his record on this issue — every parent should be outraged.’’

Gordon posted a somber note to supporters on his Facebook page and told the Globe he was upset by the mailers.

“I don’t think it’s something that should be out in the public. I think it’s so disgusting,’’ he said.

State Republican Party officials declined to criticize the mailer.

In an e-mail, state GOP spokesman Terry MacCormack said: “Rep. Day has voted more than 99% of the time with Beacon Hill Democrat leadership, supporting a toxic agenda of higher taxes and wasteful spending, and he deserves to be held accountable for his record.’’

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