An analysis of all the targets of all the jokes about public figures in the opening monologues of the highest rated late night broadcast network talk shows between August 27 to October 3, 2012:
Overall: Mitt Romney 148 jokes vs. Barack Obama 62 jokes
Worst bias: David Letterman with Romney 44 jokes vs. Obama 9 jokes
In 2008, these same late night broadcast comedians were even more biased:
1. Republican Presidential candidate John McCain 658 jokes
2. Republican Vice-Presidential candidate Sarah Palin 566 jokes
3. Outgoing Republican President George W. Bush 244 jokes
4. Democrat Presidential candidate Barack Obama 243 jokes
Source for statistics:
polination.blog 