Rick Santorum discovered this week what nearly all the other GOP presidential candidates already know – you don’t mess with Sarah Palin. Santorum touched off a media firestorm Tuesday with remarks that appeared to denigrate Palin, and the response from the former Alaska governor and her supporters was swift and unforgiving. The episode proved instructive: Not only is the Republican outline against Palin taking shape, but so too is the Palin outline for how she’ll fight back. With Palin looming as a possible contender for the GOP nomination, the question of how — or whether — to take her on...