In 1976, Gerald Ford lost Ohio by about 11,000 votes to Jimmy Carter, but chose not to challenge the result, even though a reversal would have kept him in office. (He also trailed Carter by about 1.5 million votes in the nationwide popular vote.)
This morning, Kerry trails by more than 125,000 votes in Ohio, and by about 3.5 million votes nationally, and refused to concede. What was it JFK said about Nixon in 1960? I believe it was "no class." Irony of ironies: now it applies to another JFK.