But why now, ahead of this particular primary? Wisconsin, the thinking goes, could be the leading edge of a knockout blow. Several states where the GOP electorate is more moderate, mainly in the Northeast, will hold their nominating contests in April: Maryland and Washington, D.C., on Tuesday, followed by Connecticut, Delaware, New York, Rhode Island, and Pennsylvania on April 24. These favor Romney. In Pennsylvania, Mr. Santorum's home state and a place he has vowed to triumph, recent polling shows the race to be a dead heat.