ALL THIS ATROCIOUS JOURNALISM WAS, at least to some extent, effective propaganda. The Democrats gained ostensibly impartial support for their talking point that Ryan was a liar. Bill Clinton even cited “fact checkers” in his speech to the Democratic National Convention. (That prompted an AP “fact checker” to fire back with a silly ad hominem attack: “Clinton, who famously finger-wagged a denial on national television about his sexual relationship with intern Monica Lewinsky… has had his own uncomfortable moments over telling the truth.”) The week of the DNC, a reader visiting West Palm Beach, Florida, wrote to me: “Down here in the huge building where my mother lives, all everyone talks about is what a ‘liar’ Ryan is; it’s the media diet they’re fed.”

Whether this summer is remembered as the moment when the mainstream media jumped the shark may be answered on November 6. An Obama victory in the face of slow growth, high unemployment, and Middle East turmoil would demonstrate the media’s enduring cultural and political power. But because their authority rests on the perception that it is above partisanship, further decline seems inexorable.

All the more so when you consider that it is so anxious to portray Ryan as a liar precisely because he has centered his career on telling an uncomfortable truth: that the entitlement state as currently constituted is unsustainable. That’s a direct challenge to what remains of the postwar center-left consensus. It is a truth with which the political system will have to reckon sooner or later—and from which the mainstream media and the liberal left seem determined to distract Americans for as long as possible.