I thought the MSM (particularly MSNBC) response to the “Tea Party” protests was a pretty good example of this. Noting that the vast majority of selected groups of protesters were white, (in most of the United States, geographically speaking, the vast majority of citizens are white) they subtly and not-so-subtly insinuated that the motivation behind the protests was racist anger at a Black president. Some of the MSNBC people just came out and called the protesters racist.

Of course I realize this was written long before the Tea Parties, so it doesn’t really apply. However, if you include the campaign and the primaries you can find endless examples of card-pulling.