If you watch “Real Time With Bill Maher” on HBO these days, you may have noticed something odd: the audience is booing the host.

It happens almost every week now, usually after Maher says something critical of the president. Of course, six months ago, this same audience would have cheered wildly had Maher ripped the then-occupant of the White House. Now, you’d swear from the reaction that he’d violated some taboo too weird even for pay cable.

Maher knows this. And he knows I know it. And he wants to make one thing perfectly clear.

“That” — the stand-up act — “is just an entirely different animal than the television show.”

And he does it by telling (upon request) an Obama joke.

“Now, if I (told that joke) in my studio here at ‘Real Time,’ they would probably ooh and boo. But the stand-up audience doesn’t. They don’t have that politically correct stick up their (butt). They’re really great about that, and they want to laugh.”

It might just be the difference between getting a free ticket to sit in the Bob Barker Studio to watch Maher’s comedy/talk show and dropping $40 in the expectation that the guy on stage will bust your gut every single minute.

“This is not an era where people are parting with their dollar easily, and that is on my mind from the moment I get up there,” Maher said. “I start out each show by thanking people for coming out to see me in a recession and telling them: ‘I’d better be bleeping good!’”

When I last saw Maher performing live, it was in 1996 and he was still hosting “Politically Incorrect” on Comedy Central. When I mention this, Maher invokes the deity he doesn’t believe in.

“Oh, God,” he said.

Back then, his not compelling stock routine was similar to the shtick of a lot of comedians, with observations about relationships and parents. He knows this, and he knows I know this.

“Somewhere along the line there in the early part of this millennium, I think, I really turned a corner,” he said. “I worked harder at it. So now, if people come to this show they’ll laugh a lot. And they’ll get a very comprehensive 90-minute to two-hour dissertation on the state of the world. It’s really kind of a State of the Union speech.”

To be sure, the kind of television show Maher does changed as well. He certainly does not miss the five-nights-a-week grind on ABC doing “Politically Incorrect.”

(The nervous Nellies at the network pulled the show in 2002, not long after a post-9/11 episode sparked a firestorm. Maher had dared to allow one of his guests, conservative author Dinesh D’Souza, to express the then-politically incorrect view that the 9/11 attackers were “warriors” rather than cowards. Maher not only tolerated that opinion, he agreed with it.)

“When I started ‘Politically Incorrect,’ I was in my mid-30s,” said Maher. “I was just a much less serious person in fundamental ways. And the show was less serious. I mean, you could only go so deep in a half-hour show — which, with commercials, wound up being 23 minutes — where you had to share it with four guests, three of whom on any given night were semi-retarded. I mean, it was a lot of dumb celebrities.”

“Real Time,” the now 53-year-old Maher said, “is much more conducive to what I would like to be doing: talking with only intelligent people and spending the week preparing an hour of meaningful, and hopefully entertaining, television for people who don’t have the chance to follow the news as closely as we do.”

He thinks the audience at home, which pays $13 a month for HBO, is more tolerant of his humor than the freeloaders in his studio audience. But he understands that he faces a challenge with the new president.

“Obama is a harder target now in that he’s not horny, he’s not stupid, he’s not angry, he doesn’t cheat on his wife, he’s not fat. He’s not all these things that we had in the last two presidents that were so easy to make fun of. But he’s not an infallible chocolate Jesus, either.”

He takes a comic beat, then adds: “That’s Kanye West.”

‘Real Time With Bill Maher’

When: 10 p.m. Fridays

Where: HBO