There’s obviously plenty of stuff available today about Barack Obama’s double-digit win in Wisconsin yesterday, but perhaps the most interesting analysis is by RealClearPolitics’ Jay Cost, who looks closely at the evidence that Obama, for the first time, began to win in demographic categories previously dominated by Clinton. He concludes that we may finally be seeing evidence of a “momentum effect” for Obama. But it’s a relatively small effect, and Cost thinks we won’t know for sure if it’s in play until Texas and Ohio weigh in.