PORTLAND – Most Mainers think businesses in the state should provide insurance coverage to domestic partners of unmarried employees, regardless of sexual orientation, a new poll suggests.

In a telephone survey by Portland-based Critical Insights, 57 percent of those responding said they support such coverage, while 24 percent opposed the idea and 18 percent were undecided.

Rep. Benjamin Dudley, D-Portland, is sponsoring legislation to require insurers to offer coverage for unmarried domestic partners if they offer coverage for spouses. It is designed to help the employees of small businesses, although some individual policyholders might also benefit from it.

Large employers in Maine already have access to such coverage, supporters of Dudley’s bill say.

Dudley said the poll of 403 adult Mainers, which was conducted last month and released this week, underscores the need for his bill. The poll, which asked several public policy questions, had a margin of error of plus or minus 4.1 percentage points.

Maine state government is offering domestic partner coverage for state employees as of July 1. An effort to delay it until a legislative hearing could be held failed in the Maine House.

Dudley’s bill is under attack by conservative Christian activists, who have begun organizing for a possible referendum to challenge the new state policy, Dudley’s bill or both.

The Maine Lesbian-Gay Political Alliance says opponents are incorrectly painting the domestic partner issue as a “gay issue.”

“The truth is heterosexuals are up to six times more likely to apply for domestic partner benefits than gay employees,” said David Garrity of the gay-lesbian group.

Garrity listed two reasons why. He said there are more heterosexuals who might seek the benefit, and that some gays who might qualify don’t apply because they don’t want to risk losing their jobs.