What matters in primaries: who is the most anti-Obama?

Readers of this blog know I am not usually a fan of Denver Post political columnist Mike Littwin. But, today he has written an interesting column about Romney versus Perry. He points out that at this point in the race between Hillary and Obama, Hillary, like Romney now, was much better prepared and more knowledgeable. In the end, it didn't help her, because Obama was the most anti-Bush! Likewise, Perry seems to be the most anti-Obama now, and Littwin says that is the main way to win primaries in America nowadays: be the one who is most anti-the-incumbent.