As the drought continues, the Metropolitan Water District has issued a "water supply alert" for the 19 million people it serves. Meantime, water use has become a political issue in Sacramento and Washington. President Obama will visit the San Joaquin Valley tomorrow. Republicans have focused attention there in a way that puts the Democrats on the defensive. Governor Brown — political pro that he is — is always ready to decry the effects of partisanship. So what's the potential impact of the competing proposals?