Jamison Foser, over at Media Matters, does an outstanding job of showing exactly how this is done citing a single example at The Washington Post:
Here's an example: Yesterday, The Washington Post ran an article about McCain's attacks on Obama, including his false charge that Obama's use of the phrase "lipstick on a pig" was a sexist reference to Sarah Palin. Paragraphs 1, 5, 6, and 7 contained the allegation in various forms. Paragraphs 9 and 10 were about McCain allies saying the attacks were working. Paragraph 11 finally brought the first indication that the attack wasn't true.
Constructing the article that way privileges the false claim. Readers have it drummed into their heads, over and over again, before they finally see a fleeting suggestion that it isn't true.
So how else could the Post have constructed that article? Well, the article could have begun not with an unchallenged recitation of McCain's false claim, but with a very different frame: "John McCain launched another dishonest attack on Barack Obama, the latest in a long line of claims that have been debunked and denounced by neutral observers as false, misleading, and in some cases, lies." It could have gone on to detail the growing body of evidence that McCain is running a dishonest campaign and to note that McCain risks being seen as a serial liar who will say anything to get elected.
Sound judgmental? Maybe. But it's quite consistent with coverage of Al Gore in 2000 -- coverage about things he said that were not actually false.
So we have someone running for President, who dubs all his vehicles, buses, jets, whatever, to be The Straight Talk Express, who is in truth a serial prevaricator. One would think a cub reporter would be able to write a story about the conflict and contrast of the imagery versus the reality.
Of course, they don't let cub reporters anywhere near these guys, because their are rules, or something.
Go read Jamison's whole article.