Attacks on a politician's identity - questioning Romney's religion, say, or Obama's birthplace - tend to come when an opponent is desperate and can't sell himself. ↗
Men who are engaged in public life must necessarily aim at reducing opposition to a minimum, and one of the most obvious means to that end is by misrepresenting, discrediting or ruining their opponents. ↗
President Obama has been attacking relentlessly. In 2008 he said that if you're out of fresh ideas you use stale tactics against your opponent - you try and make your opponent unacceptable and that's what he is trying to do. ↗
During the election, I had three male opponents and we went into a runoff. The front runner for the men was a native of Dallas who had run at large before, but I had a higher profile than him from my community service. ↗
I see it all the time in politics. If a candidate gets caught in a lie, he quickly tries to change the subject by throwing more mud at his opponent. The mud keeps flying until some of the slanderous material sticks. ↗