Public support for Massachusetts' health insurance overhaul has slipped over the past year, a new poll indicates, but residents still support the 2006 law by a 2-to-1 ratio. Amid a severe recession, 59% of those surveyed said they favored the state's multimillion-dollar insurance initiative, down from 69% a year ago. The poll also found that opposition to the law stands at 28%, up slightly from 22% in a June 2008 survey.