The viewer slump may signal a triumph for the Parents Television Council, a watchdog group that had blasted the series' content and accused MTV of aiming the show at underage viewers.
Based on an acclaimed British series of the same name, MTV's Americanized "Skins" depicts teens engaging in sexual activity as well as drug and alcohol abuse.
The premiere was seen by 3.3 million viewers, 1.2 million of them under 18. Since then, a number of advertisers - including Schick, Taco Bell, L'Oreal and the Subway sandwich chain - have pulled their commercials from the program.
The furor was further inflamed by a newspaper story suggesting that scenes with the series' age-appropriate actors, some of whom are minors, might violate federal child pornography laws. Last Thursday, The New York Times reported that unnamed executives at the network were concerned that the show may have crossed the line legally as well as graphically.
How Parents Should Handle "Skins"
The show's producers had been ordered to make changes to "tone down some of the most explicit content," the Times reported.
In response, MTV said in a statement, "We review all of our shows and work with all of our producers on an ongoing basis to ensure our shows comply with laws and community standards."
Monday's episode, which contained depictions of two brief sexual encounters, aired unchanged from the preview version shared with critics last month.
On Tuesday, MTV noted that the audience for "Skins" improved on its lead-in, a repeat of "Jersey Shore," by one-third. Last week's "Skins" lead-in was a new episode of the hit reality series, which drew more than 7 million viewers.
Brad Adgate, an analyst for Horizon Media, declared surprise at Monday's falloff of the "Skins" audience.
"I thought it would increase a little bit because of the controversy swirling around the show," he said.
While some audience erosion for any series on its second airing is not unusual, "50 percent is a pretty significant drop," Adgate said.
Media analyst Steve Sternberg said a contributing factor could have been a backlash to the show from parents.
"It could actually mean that a lot of parents said to their kids, 'Don't watch it,"' said Sternberg, though he allowed that "usually publicity like this benefits a program."
"Or maybe the show isn't good," he added. "People who watched the first episode and didn't like it aren't necessarily going to come back."
Sternbeg noted that 1.6 million viewers is a healthy number for MTV (though not in the league with "Jersey Shore," which last Thursday was seen by 8.9 million viewers, a record audience for an MTV series).
But what does the future hold for the season's eight remaining episodes of "Skins"?
"If the ratings hold up over the next few weeks, without more advertisers pulling out, that makes it fairly successful," Sternberg.
Adgate agreed that the fate of the show won't be known for another week or two. But his forecast was dire.
"My gut reaction is, it's in a tailspin," he said.