Again, we expect politicians to shade and shape their version of reality. But getting a reputation for doing this, as Ryan is doing during the campaign, is a particular problem for someone who has been set up as a uniquely honorable truth-teller.

Which brings us to Ryan and Norah O'Donnell today on Face the Nation. She presented him with another of the partial-truths from his convention speech, which he has repeated afterward. This is his slam of Obama for cutting defense spending, without mentioning that he has voted for these same cuts. I mention this less for what it shows about Ryan than for what it shows about O'Donnell. Take a look for yourself.

Relevant background #3. It is hard for political journalists to know enough about the substance of obscure budget votes to go up against a famed "numbers wonk" from the Budget Committee; harder still for journalists to be sure enough of their knowledge, in the real-time pressure of live TV, to say "no, that's not right" to a national figure; and perhaps hardest of all for a mainstream network correspondent to take on the responsibility of saying, "This does not seem true," rather than just finding some credentialed "critic" to quote to that effect. I've mentioned before some signs of the mainstream media groping to figure out its role in the "post-truth" era. This is an encouraging sign.

On the merits of what O'Donnell was asking Ryan about, see ThinkProgress. This is an issue I have followed. Ryan's thinly shaved rationalization here is consistent with the three I mention from his convention speech, in that each involves the deliberate omission of a major, elephant-in-the-room complicating truth. And, before you ask, when Joe Biden, Barack Obama, or other Democrats go as far as Ryan has -- not in presenting their opinions, or political "visions," but offering gross distortions-through-omission of their own records -- they deserve exactly the same treatment.

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* I edited this to include "a big part," since the debt-ceiling uncertainty was a factor but not the only factor S&P mentioned.

