House Democratic leaders proposed a new compromise Tuesday that calls for installing electronic highway tolls for trucks only on a dozen bridges across the state in the latest chapter in the long-running debate at the state Capitol. In return, Gov. Ned Lamont is expected to support using a portion of the state’s rainy day fund to help finance his 10-year transportation plan — but far less than the $1.5 billion proposed last week by Senate Republicans. House Speaker Joe Aresimowicz and House Majority Leader Matt Ritter are seeking tolls on 12 bridges that were outlined in Lamont’s plan. Two toll sites have been dropped — on Route 9 in Middletown and on the Merritt Parkway, where trucks are not permitted. Their proposal would raise an estimated $150 million per year. Along with money from the rainy day fund, the plan is expected to generate enough money to pay off low-interest federal loans.