At a minimum, Hillary Clinton must win one state, the most likely is Indiana, as Barack Obama has held big leads in the polls in North Carolina.

Then we get to the Pennsylvania question, which was how big must that winning margin be? I'm sure Team Clinton will say things like, "A win is a win" once again.

But the real question about "margin" may be about delegates that night. Even if Clinton wins one state, Obama could well increase his delegate lead by swamping her in North Carolina.

At this point, it is Clinton that needs to be gaining on Obama. Going in reverse is not a way to win the Democratic nomination, especially with the number of available delegates dwindling each week.

Still, I bet if Clinton wins in Indiana, she will go on into West Virginia, which votes on May 13, where she will be heavily favored. A win there sends her on to May 20, where she's favored in Kentucky.

Obama again increased his delegate edge on Thursday by adding one more superdelegate, Rep. David Wu of Oregon. His state votes on May 20 along with Kentucky, but Wu decided to cast his lot now.

That gives Obama a 3-1 edge in superdelegates since his loss in Pennsylvania on Tuesday. That is not exactly a "Formula For Victory" for Hillary Clinton, as she needs to grab just about three of every four of the 300 or so superdelegates that remain uncommitted.

Clinton campaigned in North Carolina on Thursday - check that - she campaigned in the Tar Heel State on Thursday afternoon, as I was a bit surprised to see her on the Senate floor around lunchtime.

Obama meanwhile took another day off the campaign trail, as he spent another night at home in Chicago.

Today he's back on the trail in Indiana, which certainly has morphed into the Showdown State for May 6. A win there and a win in North Carolina and this race is over.

Of course, it may already be over, but Obama still hasn't landed that knockout punch. And as in boxing, there's always the chance that your opponent just might catch you with a haymaker in the 14th or 15th round.

That's why I don't expect any more debates between these two Democrats. Obama has nothing to gain and everything to lose