The measure, called Question 3, prompted heated debate in the months leading up to the election. Central Maine Power and Versant Power, the state’s dominant utilities, poured more than $40 million into a campaign opposing the referendum, outspending Pine Tree Power advocates 34 to 1. Political groups funded by the utilities and their parent companies mailed flyers and aired ads on TV, radio, and social media, urging Mainers to reject the measure, which would have effectively put the two companies out of business.