National Journal: Environmentalists need Mary Landrieu, but they don't love herand they're proving it with their checkbooks. Louisiana's Democratic senator and Republican Rep. Bill Cassidy are locked in a Bayou battle that will go a long way in determining whether Democrats can hold their imperiled Senate majority, a force that has proved an implacable bulwark against a steady stream of House Republican attacks on environmental regulations. But that hasn't convinced the environmental lobby's heavy hitters to cut...