Politicians want voters to have a positively-biased view of themselves. Consequently, voters learn more about politicians from their failings than from their good deeds.
Barack Obama, for example, smokes. If being known as a smoker was politically beneficial to a candidate then we couldn’t know if Obama really enjoyed smoking or if he was just pretending to enjoy smoking to appeal to voters. But because being known as a smoker will probably hinder Obama’s political career, we know that he really wants to smoke. Consequently, Obama’s smoking reveals something about his character. Perhaps, for example, it shows he is not very future oriented and is willing to suffer long-term harm for a short term benefit.
Newt Gingrich has admitted to having had an extra-marital affair whereas Hillary Clinton appears to have been faithful to her husband. Perhaps Hillary Clinton really wants to cheat but for political reasons either hasn’t or has covered up her infidelity. We can’t be sure, therefore, if Hillary Clinton has the type of character that causes her to remain faithful. Since his infidelity will certainly not help his political career we can be sure that Gingrich wasn’t just pretending to be unfaithful or wasn’t being unfaithful just to gain political advantage. Rather, given his character being unfaithful maximized Gingrich’s lifetime happiness. This infidelity, therefore, provides considerable unbiased insight into Gingrich’s character.
Finally, it was recently revealed that Al Gore’s mansion uses 20 times as much energy as the average American’s home does. If Gore personally used much less energy than most Americans did we couldn’t be sure if he was doing this because he genuinely cared about the environment or if he merely wanted people to think he cared about the environment. In contrast, since his large energy use harms him politically, we can be sure that he didn’t use vast amounts of energy just to help his political image. Rather, given his character it is in Gore’s self-interest to use huge amounts of energy even though such considerable energy use will cause others to think he is a hypocrite.