• by Wayne Friedman , March 20, 2009

CBS' first day of the March Madness NCAA basketball tournament improved its usual disruptive Thursday work--while President Obama dramatically shook up late-night numbers at the end of the evening.

Obama became the first sitting president ever to appear on "The Tonight Show"--grabbing an eye-opening 11.2 preliminary household rating at 11:35 p.m., matching the fourth-best rating in Jay Leno's 16 years hosting the program. CBS pulled a Nielsen preliminary 3.5 rating/10 share among 18-49 viewers, tying it with ABC. Not only that, but both networks had the exact same numbers among 18-34 viewers: a 3.1/10.

Earlier in the evening--where CBS is normally strong in terms of overall prime-time viewer numbers--this time, ABC came out on top: 10.7 million for ABC and 9.4 million for CBS. It was all because of CBS' big sports event, which typically skews more heavily to a male audience.

ABC got dinged with its big Thursday 9 p.m. to 10 p.m. player, "Grey's Anatomy" at a 5.0 rating/12 share, which looks to match its lowest-ever 18-49 performance. CBS' "NCAA Tournament" took in a 3.7/10 during the 9 p.m. hour.

NBC's half-hour of "The Office" had the second-best results during the time slot with a 3.9/10, and it tied "Grey's" among younger viewers 18-34, at a 4.4/12. "Office" slipped one-tenth of a rating point among 18-49 viewers from the week before. So did NBC's "30 Rock" at 9:30 p.m., which came in at a 3.2/8.

Fox fared pretty well. "Bone" moved up to a 3.0/10 from a 2.8/9 the week before, while "Hell's Kitchen" at a 3.5/9 stayed the same.

At 10 p.m., ABC put in a strong performance with "Private Practice," up to a 3.9/10 from a 3.5/9 the week before. "Practice" was a half a point better than the "NCAA," which landed with a 3.4/9. Without George Clooney and other "ER" alumni performers, NBC's "ER" went to 3.3/9 from a 3.9/11 the week before.

CBS lost ground week-to-week from a 3.7/10 to a 3.5/10, but thanks to the young men who watch college basketball, it picked up big-time among young viewers--grabbing seven-tenths of a rating point more this week, up from a 2.4/7 the week before.

After CBS and ABC, Fox came in at third place among 18-49 viewers with a 3.1/9;, NBC at 3.0/8, Univision at 1.8/5, and CW at 1.3/4.