The drawbacks to the internet in regard to politics are:
Overexposure of candidates: it common place for people in politics to be very transparent. This leads to disclosure of privacy and everything about the politician to the public. This act can be a very dangerous one for security reasons. Some candidates can be favored also by the way the internet exposes them.
Misinformation: the internet is one of the largest source of unverified information. Politicians are often seen sponsoring propaganda about other candidates just to raise their own social acceptance.
Partisan dialogue: most supporters are often biased and not logical enough about who they support.