Barack Obama's strong showings in Wisconsin and Hawaii last night netted him an additional 18 delegates, his campaign estimates, giving him a net lead of 159 pledged delegates. That lead, Obama chief David Plouffe suggested on a conference call this morning, is difficult, if not impossible, for Hillary Clinton's campaign to overcome. "We have opened up a big and meaningful delegate lead," he said.

To net that many more of the 1,000 or so pledged delegates remaining, "they need to win going away," Plouffe said. "The only way, in this system, to win delegates is by big margins." He estimated that, because of delegate selection rules in Ohio and Texas, the Clinton camp would have to win both states by as many as twenty points to win significantly more delegates than Obama.

Time, Plouffe said, is on Obama's side. "There's no doubt Senator Clinton started this [campaign in Ohio and Texas] with a big lead," he said. But "we're looking forward to a lot of time on the ground, which is a luxury we have not had" since January. Indeed, in many cases, Obama has been able to cut into Clinton's lead when he's had time on the ground. With two full weeks before Buckeyes and Longhorns vote, Obama has plenty of time to spend on the ground.

Even with big leads, though, Clinton might wind up with a bad election night. Exit polls from Wisconsin and earlier contests have started showing voters who had otherwise favored John Edwards, chiefly lower-paid white men, breaking hard for Obama once their guy was out of the race. In Wisconsin, Obama won white men by twenty-one points.

While women still make up the majority of the Democratic electorate, Obama looks to have muted Clinton's lead among them while racking up big margins among men. Having made such significant inroads in earlier states, Obama's path to victory -- real or in the expectations game -- in Ohio and Texas becomes much easier.

Plouffe declined an opportunity to offer a full-throated response to criticism yesterday from John McCain, who attacked Obama as offering an "eloquent but empty call for change." Plouffe said McCain would offer what he characterized as a third term for President Bush, but that time remains for their differences to be explored. "The general election is going to be a long general election, and we don't have much control over when that starts," he said.