McCain Cries Foul

You need to be careful with what you say on the campaign trail. There are tens of millions of people just waiting for you to goof up. The most recent case is Barack Obama twisting McCain's words, (McCain had said on a television interview that we have had great progress with the economy over the past seven and a half years), to say that he is pleased at how the economy is going under George Bush. In my opinion, Obama hit the interpretation right on the head. McCain has been known to back President Bush on many subjects, [The war in Iraq (Hey, he'd even be happy with the troop levels for 100 years)], why stop backing him now?
Barack Obama is using McCain's slip-ups to his advantage, and I see that as a good campaign strategy. Although it may be frowned upon by a majority of the conservative voters, I cannot remember a time when a candidate didn't twist someone else's words or actions.
Do you agree with these types of strategies? Why or why not? Can you recall any "memorable" times this has happened?