Reader Kim B. lays out a scenario that strikes me as largely correct:
If Obama can win enough delegates Tuesday to just keep it close enough to stay in the game then the calendar in the period before March 4th sets up pretty well for him.
The next contests are spread out and give him a chance to build momentum once again leading into March 4th. To wit: Feb 9: Washington caucus (he does well in caucus states, and Seattle is educated, upscale mecca) Feb 12: Virginia is diverse, with Tim Kaine endorsement. Maryland is diverse, big black vote. DC is his for the taking. This one night alone will bring Big Mo on TV (a Tuesday night in prime time). Feb 19: Wisconsin is anti-war, lots of students. Obama could compete here. Hawaii on same night gives him padded win and nice personal storyline.
That's it until March 4th. He could go in to that date with renewed momentum. Because of this I predict Clinton team will challenge him to a series of debates in the period between Tuesday and March 4th. They can't let him float back up like this. Key to the whole thing is to not get blown out on Tuesday - split just enough delegates with her so the media keeps him "in the game." After Tuesday Clinton team may have to face the fact that he is still alive while many of her big states (NY, NJ, CA, MA, FL) will now be in the rearview mirror...
March 4, of course, sees Ohio and Texas hold their primaries.
Kim's basic point, though, is that regardless of what happens on Feb 5 (unless there is a blow up,) the rest of February favors Barack Obama, and March favors Hillary Clinton. That means that there's almost no way either candidate will throw in the towel before then, and the pressure on February will be on Hillary Clinton to set expectations correctly and keep a slim delegate lead as Obama racks up victory after victory.