By now you have probably heard about the ringers at the CNN debate. If not Glen Reynolds has a few links to get you started. Eric also has some help. The short version: The Democrats had party activists asking questions for the Democrat's debate and they had party activists asking questions for the Republican's debate. So of course the Democrats got softballs and the Republicans got toughies. Which is a good thing. It takes the Republican's minds off of intraparty warfare and focuses it on beating the Democrats.
As to CNN and the Democrats:
It is unwise to attribute to malice alone that which can be attributed to malice and stupidity.
There is also the apocryphal Grey's Law:
Any sufficiently advanced incompetence is indistinguishable from malice.