Why has American politics become a exchange of insults?

American politics, a stew of chaotic insults. Why do presidential candidates focus so much time and resources on bashing the other candidate? One might think that the struggle for power in becoming president is a higher priority for these candidates than focusing on their goals and ambitions for when they get into office. Do they really have America's best interests in mind, or do they just want their own room in the White House?

When did many Americans start valuing a candidates ability to tear down the image of their opponent greater then valuing what they believe America needs to build and grow? This can been seen many times this election, through ads on TV to the debates between Clinton and Trump. Many ads are funded that just to make a candidate look bad. In a ad called "She knows Putin too well", the video presents facts of what Clinton has done to help the Russians, questioning what more she might do to aid the Russians if she becomes president. In another example, Clinton released an ad questioning what Trump might do to the daughters of families if he becomes president. It shows a series of shots of young women, in between footage of Trump saying insulting thing about women. Why are resources spent on these kinds of ads?

 Why are people debating the scandals of the candidates, instead of the ideas that each of them has for how they could help America advance? A example of this could be seen in Hillary's private email scandal, or Trump's woman abuse scandals. News seems to be absorbed by these scandals as well. The internet is swarmed with news articles telling the new exciting scandal that they may or may not have found on a person. In contrast, this is the sort of stuff that many people want to see, and therefore more and more of these stories are released.

Candidates now need to spend much more energy making sure they don't trigger anything that could cause another rumor, taking away from arguing the issues and solutions they want to bring to America.