The group spearheading the campaign seeking to legalize same-sex marriage in Maine has come out with a new television ad. Mainers United for Marriage launched a 30-second ad Monday featuring a group of four volunteer firefighters, one of whom is gay, from York. In the ad, the firefighters talk about the bond that exists between first responders, whether they are straight or gay. The ad will run for seven to 10 days in the Portland, Bangor, and Presque Isle television markets. Mainers United has aired two commercials in support of the Nov. 6 ballot question that will ask voters if they want to legalize same-sex marriages.