With the backing of religious leaders and enviros, a group of lawmakers in Connecticut said yesterday that they have the votes to force the state’s five oldest, dirtiest power plants to clean up. For the past two years, legislators have tried and failed to impose tighter air pollution limits on the plants, which are exempted from federal Clean Air Act rules by a loophole that lets old power plants pollute more than new ones. A new bill, which lawmakers expect to send to Gov. John G. Rowland’s (R) desk before May, would require the plants to meet the latest emissions standards by 2003. The five plants account for nearly half of the air pollution emitted by major industrial sources in Connecticut, according to Brooke Suter of the Connecticut Coalition for Clean Air.