Stephen Colbert’s “testimony” before Congress last week was a clear sign that ironic rot (if you’ve got a better term, let me know) is sinking into the foundation of our political system.

Irony, or post-irony, or ironic post-whatever has been metastasizing through the culture for decades. The most famous example was Seinfeld, a hilarious show that was famously “about nothing” and much derided by earnest writers on the left and right for its detached mockery of any deeply held principle or conviction.

But it hardly began with Seinfeld. David Letterman launched a talk show that made fun of talk shows. Before that, Saturday Night Live crafted brilliant fake commercials and newscasts (which, sadly, are the only reliably funny parts of the show these days).

In the 1990s, Washington fell in love with Hollywood in an unprecedented way. In countless films, politicians, reporters, and pundits played themselves. There was also an influential — and occasionally funny — sitcom called Murphy Brown that jumped back and forth from make-believe to reality. Things got particularly confusing when Vice President Dan Quayle criticized the show for glamorizing out-of-wedlock births, and the show’s creators responded by having the fictional Murphy Brown whine about personal attacks on her lifestyle.

Things got outright weird with the creation of The Daily Show, a fake news program hosted by Jon Stewart since 1999 that often provides some of the best (and occasionally the worst) criticism of American politics and is revered on the left as somehow newsier than news. For what it’s worth, a senior Republican congressman told me that a Daily Show piece on the GOP “Pledge to America” was the only one that drew blood.

The Daily Show begat The Colbert Report, in which Colbert plays a jingoistic, know-it-all borderline bigot whose standard for veracity can be summarized with the word “truthiness.”

In other words, he pretends to be what many liberals claim Bill O’Reilly is. That’s the joke. Get it?

It was this Stephen Colbert who was invited to testify before a House judiciary subcommittee on immigration and labor. It was an excruciatingly inappropriate spectacle. “This is America,” Colbert inveighed. “I don’t want a tomato picked by a Mexican.”