AUGUSTA, Maine — Former Gov. Angus King has a wide lead over his Democratic and Republican rivals in Maine’s U.S. Senate race, and supporters of same-sex marriage have an edge in their November contest, according to a new poll released Monday.

King, an independent who was Maine’s governor from 1995 to 2003, had 50 percent support in the poll, which was conducted by the MassINC Polling Group for the Boston public radio station WBUR.

Republican candidate Charlie Summers, Maine’s secretary of state, trailed King with support from 23 percent of those surveyed. Democratic candidate Cynthia Dill, a state senator from Cape Elizabeth, had support from 9 percent.

The poll asked 506 likely voters about their preferences in the two days following last Tuesday’s primary election, when Summers and Dill were chosen as their party nominees. The poll’s margin of error is 4.4 percent.

While the survey probably isn’t predictive of how the Senate race will look in a month, the results should be cause for concern for Dill and Summers, said Amy Fried, a political science professor at the University of Maine and a Bangor Daily News columnist and blogger.

“I think they’re both going to have a difficult task in raising money with these poll numbers,” she said.

And they’ll likely need that money if they want to raise their name recognition among voters, Fried noted. Thirty-five percent of those surveyed had never heard of Dill and 23 percent hadn’t heard of Summers. Still, Fried said, higher recognition may not be enough to overcome King’s lead.

King was the choice of 60 percent of Democrats, 31 percent of Republicans and 57 percent of independents.

Summers, in a statement from his campaign, said the poll “primarily reflects underinformed name ID,” and that the more important polls will be those conducted in October.

Dill said in a statement, “We have work to do, and are prepared to do it.”

King’s campaign declined to comment on the poll results.

In addition to posing questions about candidates, the poll also gauged support for a measure on November’s ballot that would allow same-sex marriage in Maine.

The survey found that 55 percent of voters supported a law that would allow same-sex couples to marry and “protects religious freedom” by not requiring clergy to perform same-sex marriages. Thirty-six percent of respondents were opposed.

The WBUR poll was completed the day Maine’s secretary of state released draft wording for the ballot question that simply asks, “Do you want to allow same-sex couples to marry?” and does not include language about protecting religious freedom that same-sex marriage supporters had sought.

Supporters of the same-sex marriage ballot initiative celebrated the poll results, saying that they figure into a continuing trend of voters changing their minds to endorse marriage for same-sex couples.

“More and more people agree that all loving and committed couples should be able to marry,” Matt McTighe, campaign manager for Mainers United for Marriage, said in a statement.

But opponents called the polling question “biased” and questioned the survey’s validity.

“Polling on the issue of marriage has notoriously been wrong,” Bob Emrich, chairman of Protect Marriage Maine, said in a statement. “In spite of the rhetoric from opponents of protecting marriage between one man and one woman, we are confident that we will prevail in this fight just as we did in 2009.”

The survey also found commanding approval for Maine’s two current U.S. senators, Snowe and Susan Collins. Snowe and Collins, respectively, had 82 percent and 80 percent favorability ratings in the survey; both had 9 percent unfavorable ratings.

Some 41 percent of those surveyed viewed Gov. Paul LePage favorably, compared with 50 percent who didn’t have favorable views of the Republican governor. The survey put his job approval rating at 40 percent, with 49 percent disapproving.

The WBUR poll results were not dramatically different from the results of a poll conducted for the Maine People’s Resource Center more than two months ago, before Democrats and Republicans had chosen their nominees.

In that survey of 993 registered voters, King had 56 percent support, and Summers had backing from 22 percent. The poll didn’t ask about Dill, but found 12 percent support for Democrat Matt Dunlap, who lost to Dill in last week’s primary.

While the primaries have taken place, there still have been no major events to change the race’s makeup, said Fried.

“If there really starts to be a lot of effort to make the case against Angus King, or these other candidates making their own case, that might certainly lead to an opinion change,” she said.