“Late Show” viewers must be starting to wonder whether David Letterman hates old people or just John McCain.

Maybe more important, is the host having a hard time hiding his support for Barack Obama?

Take for example Thursday’s opening monologue. As the topic changed to the presidential campaign, Letterman focused most of his comedic attacks on the GOP frontrunner and also-ran Ralph Nader while actually not offering one joke about Barack Obama.

For those interested, here was the joke tally from Thursday’s monologue:

* Ralph Nader - 7
* John McCain - 6
* Hillary Clinton - 2
* Barack Obama - 0

You think Dave and his writers might be Obama backers, or was ignoring the current favorite to win it all just an innocent oversight?