"We're not going to be able to eat more hot dogs than Rockefeller," said a New York Democratic county chairman last week. "We're going to present a serious, dedicated candidate. It'll be a campaign of contrasts." It may at that. To run against ebullient Republican Governor Nelson Rockefeller, one of the few serious U.S. politicians who can smile handsomely with a mouthful of wieners, Democrats have just about settled on an earnest lawyer with rimless glasses, a furrowed forehead and a rumpled Brooks Brothers suit. The prospect: U.S. Attorney Robert
Morris Morgenthau, 43, son of F.D.R.'s Treasury Secretary Henry Morgenthau...