Psyringe: Because it works. Analyses have shown that trying to throw mud at your opponent is often more effective than trying to convince voters of one's own vision. At least in the US, where the respective studies were done, it might be different in other parts of the world.
keeveek: This is kinda sad, isn't it?
But it doesn't always work. Major Polish opposition party focused their entire campaign on bashing over opponents and it didn't give them nothing. They had exactly the same result as ratings were from the beginning.
Yes, it's _very_ sad imho. A democracy in which slander is the most efficient way to get you to the top is pretty much defunct, since the competition of ideas that _ought_ to be the strength of a democracy gets distorted and marginalized.
Like in Poland (from your example), I doubt that such a strategy would be very successful in Germany right now. Generally, attacking one's opponent in such an obviously unfair way would be regarded as a very poor style, and it would raise the question whether the campaign was so little convinced of their own agenda that they are spending money to attack the opponent on a personal level. But I don't know whether that'll still be the case in, say, 20 years from now. In many respects, European culture "catches up" with American culture within 1-2 decades.
The groundwork is already laid. Back in the 70s and early 80s, German parties tended to put their actual _agenda_ on their posters. Nobody does this anymore. Today, posters typically show the face of a party's lead candidate, and some catch-all slogan that's supposed to highlight popular traits of their personality. So, while we don't yet have the circus going on that elections in the US have degraded to, we _are_ eroding our political culture nonetheless.