Conan O'Brien had a triumphant debut on Monday night. His new TBS talk show, "Conan," pulled in 4.3 million viewers, while just 3.5 million tuned into his nemesis Jay Leno's "Tonight Show" on NBC. O'Brien also "towered over" David Letterman, Jon Stewart, and Stephen Colbert, whose shows pulled in 3.4, 1.3, and 1 million respectively. That said, preliminary numbers for O'Brien's follow-up show — on Tuesday night — suggest that "Coco was king for just a day." His ratings fell by a third, placing him below Leno and Letterman, but not Stewart. (Watch a Fox Business discussion about Conan's ratings.) How significant is the drop? Critics put it in perspective:

This was inevitable: Don't look now, but the air may be coming out of Conan's ratings blimp — and quickly," says Dylan Stableford at The Wrap. Everyone knew Conan's numbers would dip "once the curiosity factor wane[d]." It appears "the curiosity was short-lived."
"Conan's ratings dip on night two"

Demographics could matter more than total viewers: It's highly unlikely that O'Brien would keep beating Leno and Letterman in absolute viewers, says James Poniewozik in Time. When you break down those first-night numbers, however, it's clear that Conan attracted far more younger viewers — the ones advertisers value most. The average age of Conan's viewer was 30, compared to 56 and 54 respectively for Jay and Dave. If this "demographic pattern holds, that could be trouble for the big-network shows going ahead."
"Conan night one beats networks, by stealing their young"

And he's still king on cable: Many say Conan's real competition isn't Leno and Letterman but his cable brethren, Stewart and Colbert, who attract a similarly young, media-savvy audience. He "has a chance to upstage them, at least initially, because of the timing for his launch," says Nellie Andreeva at Deadline. "The Daily Show" and "The Colbert Report" both "thrive in busy political times." Now that the midterm elections are over, "there is enough political fatigue to give Conan an opening."
"UPDATE: 4.2 Million watch Conan's debut which beats Leno, Letterman, Stewart & Colbert"