Obama gives Letterman biggest audience in 4 years

An appearance by president Barack Obama gave David Letterman his largest overnight rating in four years.

Monday's season-opening episode of CBS' "Late Show" received a 5.6 metered-market household rating and 14 share -- a dizzying 195% higher than NBC's "Tonight Show with Conan O'Brien" (1.9, 5).

Not that it matters (except it makes a nice talking point), Letterman also beat NBC's 10 p.m. "Jay Leno Show" by 27% among households. The last Letterman episode to post a higher rating was when Oprah was his guest in 2005.

Note though, when Obama was on "Tonight" back in March with Leno at the helm, the NBC show received an 11.2.