Mitt Romney has run a smooth, low-drama campaign so far, but its aggressive posture toward Rick Perry within the past week leaves me wondering about his strategic choices. …

But it is precisely because Mr. Perry is the more threatening candidate that Mr. Romney might want to think twice about helping to position Mr. Perry as the “anti-Romney” choice — a valuable piece of real estate that candidates from Mr. Perry and Mr. Cain to Tim Pawlenty and Jon M. Huntsman Jr. have long tangled over.

Part of this is simply that any type of negative campaigning tends to entail more risk than positive campaigning, and candidates with as strong a strategic position as Mr. Romney’s should be loathe to take risks.