PORTLAND — The coalition spearheading a campaign seeking to legalize same-sex marriage in Maine has opened three new field offices and relaunched its door-to-door efforts to build support.

Mainers United for Marriage has opened offices in Brewer, Lewiston and Portland. A fourth office will open next month in Kennebunk.

The group is leading the campaign in favor of November’s statewide referendum asking voters if they want to legalize same-sex marriage.

The coalition says its staff and volunteers are now going door to door to persuade residents to vote in favor of the referendum.