Ken Mehlman is the unflappable efficiency expert who chairs the Republican National Committee. Because he's not known for histrionics, his warning last week to GOP congressional staffers about this November's elections caused many on Capitol Hill to bolt upright. Mr. Mehlman traveled to Capitol Hill to warn the staffers that they risked a disaster at the polls if they didn't pass meaningful legislation the conservative base cares about. Other GOP strategists go even further. "If the election were held today, I'd say the odds are 90% that we'd lose the House," says GOP consultant Mike Murphy. Other Republicans aren't as...