Stephen Colbert is a comedy genius because he’s perfected the art of saying the opposite of what he believes.

That’s right: Stephen Colbert invented sarcasm.

So huzzah for the trailblazing, game-changing, water-cooler-conversation-generating new comic visionary taking over David Letterman’s chair.

Except Colbert essentially does the same joke over and over (conservatives are morons) and he’s only funny if you accept the premise (conservatives are morons) while you snort Mountain Dew out your nose thinking about what an awesome point he just made. (Conservatives are morons.)

Colbert’s audience is young, but his act gets old after about five minutes, and his legendary ability to “stay in character” is a myth.

What he does is split himself into two personalities. One issues standard liberal boilerplate gleaned from whatever fanciful view of reality is being peddled on Daily Kos or the Huffington Post. No conservative would ever say these things in the first place.

Then he rebuts himself. His brilliant breakthrough technique? Say whatever a dumb guy would say.

This is taken as genius not because it’s original to do dumb-guy shtick but because Colbert is framing his dumb guy as a conservative dumb guy. See the revolutionary-ness? Of doing what Carroll O’Connor did as Archie Bunker 40 years ago? Liberals are confusing the nice buzz they get when their hate circuits are stoked with actual smart comedy.

Colbert is supposedly one of those meta, self-aware comics, but he doesn’t register how absurd it is for the viewer to watch this split personality arguing with himself.

Because comedy doesn’t work unless the underlying premise rings true, just about no conservative finds Colbert funny. So, though he will be dropping the faux-con shtick when he takes over Letterman’s chair, millions of conservatives won’t be watching.

CBS is essentially writing off half the potential audience before the first episode even airs.