Casino opponents swept the town selectmen’s race on Monday in stark public rebuke of Wynn Resorts and the casino developer’s plans to build a billion-dollar gambling resort across from Gillette Stadium. Though the casino proposal from Las Vegas mogul Steve Wynn was not on the ballot, the issue dominated the campaign, and the race came to be seen as a referendum on the project. The vote shifts the five-member board further against the project, with four selectmen opposed to the casino and just one willing to entertain more information on it.