As the political battle over same-sex marriage plays out in state capitals across the country, several California companies have emerged as the go-to players for opponents of the marriages.

One of the companies, Mar/Com Services Inc., lists its business address here in San Francisco, a city well known for its large and politically active gay population. When Maine residents opposed to a new law permitting same-sex marriage decided earlier this year to challenge it, they hired Mar/Com to do the production work for the television and radio advertisements.