HARRISBURG, Pa. (AP) — The natural gas boom that has hammered coal mines and driven down utility bills is hitting nuclear power plants, sending multi-billion-dollar energy companies in search of a financial rescue in states where competitive electricity markets have compounded the effect.

Fresh off victories in Illinois and New York, the nuclear power industry is now pressing lawmakers in Connecticut, New Jersey, Ohio and Pennsylvania for action. Lobbying efforts are bubbling up into proposals, even as court battles in Illinois and New York crank up over the billions of dollars that ratepayers...