Democratic National Committeewoman Debbie Dingell, wife of Rep. John Dingell (D-Mich.) speaks at a United Auto Workers hall in Detroit, Jan. 12, 2008. (The Washington Post) Updated 1:05 p.m. By Jonathan Weisman Debbie Dingell -- Washington doyenne, General Motors powerhouse and the wife of House Energy and Commerce Chairman and Hillary Clinton supporter John Dingell -- endorsed Barack Obama today, the clearest sign yet that the long-awaited flood of superdelegate endorsements is coming. Dingell's endorsement came along with that of another Michigan Democratic National Committee member and superdelegate, Rick Wiener. They followed nods from House Majority Whip James Clyburn (D-S.C.) and Congressional Black Caucus Chairwoman Carolyn Cheeks Kilpatrick (D-Mich.), Rep. John Olver (D-Mich.) and two other superdelegates. On a conference call announcing his own endorsement, Rep. James Clyburn named three more undecided officials who, he says, will endorse Obama today: Rep. John Spratt of South Carolina, New York superdelegate Ralph ...