In the pre-Internet world, sliming a political opponent was fairly easy to do. You would get some well-known media figure to trumpet his or her "discoveries" about the opposing candidate and you would time it so there was no time for anyone to respond with the whole story.
Most of the media figureheads on the Left and the Right still are working on that assumption, even after Rathergate.
Unfortunately for them, bloggers can locate the original transcripts on the "Intertubes" and publish corrections to false stories and misleading headlines within hours of the original slime. They also use factcheck.org to get the entire story and so can you.
Result? Extreme loss of credibility by the misleading media figure and a boost for the target of the slime.
A political campaign is a high level marketing activity and obeys the same fundamental rules of communication. If a group maligns a political opponent or even spends a lot of time discussing a political opponent, that group is spending their precious donated money advertising the opponent.
When a false statement is made, it can be easily detected through use of the Internet and the originator of the falsehood is tagged as an "unreliable source" meaning untrustworthy. Increasing the volume of the lies told is no use. It only makes those who are uncommitted more wary of your candidate.
Listen to the candidates yourself and understand what they are saying. If you listen to news, try to understand that 85% of all media figures vote for one political party. That is not wrong at all, but you should be aware that 85% is a long way from being fair and balanced.
As Election Day nears, there will be more pressure on all sides to support the "party" candidates. and the truth will get bent more and more. As a citizen, you will be better off finding out for yourself what the candidates have done and said.
If you find that you are enraged by what some candidate is supposedly going to do to the Constitution, the American Way, women’s rights, your taxes, read factcheck.org first before sending emails to everyone you know. Chances are that the candidate never said or did what was claimed by opponents.