Late-night ratings sank over the past three months, despite the attention and extraordinary television created over the winter by the drama of Leno taking back “The Tonight Show” from Conan O’Brien.

“Late-night talk shows have been around since the 1950s, and you wonder if they are getting passe with the viewing public,” said Brad Adgate, an analyst with Horizon Media.

Competition is a factor. Johnny Carson in his prime never had to worry about a Jon Stewart or George Lopez. Or video games and the Internet. Or, for that matter, his own network. At 11:35 p.m., more people now watch programs saved on their digital video recorders than either Leno and Letterman, the Nielsen Co. said.

Back at NBC, Leno averaged 4 million viewers a night during April, May and June. That’s a full 1 million viewers lost to NBC compared to the same three months in 2009. Letterman wasn’t necessarily the beneficiary, since his audience of 3.3 million people was off 7 percent from 2009.

An hour later, NBC’s Jimmy Fallon and CBS’ Craig Ferguson are both down, with Fallon’s nightly audience of 2 million last year slipping to 1.64 million. Comedy Central’s Stewart and Stephen Colbert are essentially drawing the same numbers as last year.

TBS may be excited about O’Brien bringing his fans over this fall, but they may want to pause at Lopez’s numbers. Lopez, who has the time slot O’Brien will take over, saw his numbers dip by 20 percent to 820,000 a night.

Bright spots are ABC’s Jimmy Kimmel, who was aggressively promoted by his network this spring, and E! Entertainment’s Chelsea Handler. ABC’s “Nightline” is also up slightly in viewers and consistently beats Letterman.