The Curse of Unethical Immoral Leaders
We don't know why this should be the case, but it does seem that left-wing governments and political parties have a perpetual nastiness about them.
Over time this creates rising political risks since demonising your opponents means that all they have to do is show up to the electorate as reasonably normal people and in an instant two things happen. The first is the credibility of the slanderous overkill party goes up in smoke. The second is that the electorate find those so excessively slandered to be much better than expected. He or she turn out to be a pleasant surprise.
Obama and the Democrats in the United States appear to have fallen into this trap.