Conan O'Brien had big shoes to fill when he took over for Jay Leno as the host of NBC's highly-rated Tonight Show. So far, it looks like he may be a few sizes too small. Although Conan is a major hit with the 18-49 year old demographic—likely why he was chosen as Leno's successor—the program has seen a relentless drop in ratings since it first aired with its new front man. Conan, who was chosen by NBC to take over Leno's spot five years ago, has seen the Tonight Show outperformed by rival late-night host David Letterman, who took first place in the timeslot for the first time on June 9th with 3.38 million viewers to O'Brien's 2.93 million. That's down from Conan's launch on June 1, when 7.12 million viewers tuned in, and soon quickly tuned out. "The trend is relentlessly downward," said one source to the New York Post. "But NBC will never admit they made a mistake."