Nixon was more qualified to be president than Kennedy in 1960. He took his work more seriously and earned everything he had, as opposed to Kennedy’s sense of entitlement. Kennedy was barely younger but looked much younger and he was far more comfortable in front of the camera. He probably won because of the televised debates.
Carter was much younger than Ford and had a full head of hair at the time. Ford was winning the election until they went on TV together. When Carter was the incumbent he was winning until he went on TV with Reagan, a former actor. Reagan won in a landslide.
Dukakis lost to the first Bush largely because he seemed distant on TV. He was also a hairy Mediterranean immigrant’s son running against a Connecticut WASP from a political dynasty.
The first Clinton was a generation younger than the first Bush and looked a lot better on TV. He was more charming and more articulate. Women wanted to sleep with him. And many did. Nobody wanted to sleep with Bush. Clinton easily won.
Obama looked young, charming, non-threatening, articulate. McCain looked old, crippled, sometimes mean. Who did you expect to win?
Gordon Brown's official Downing Street portrait