My radio informs me that Kucinich has withdrawn from the race for the Democratic Presidential nomination in the face of pressure to focus on getting re-elected in his own Congressional district and in light of the fact that he has no realistic chance of getting more than a handful of delegates to the Democratic National Convetion, out of several thousand. This is unexpected, but not very consequential.
This leaves in the race Clinton, Obama, Edwards and Gravel. Gravel's performance in polling and the delegate count is even weaker than Kucinich's -- he is a non-entity in the race whose eventual departure will be largely irrelevant.
Edwards seems unlikely to make it out of third place in South Carolina or really, anywhere else, and hence he is almost certain to not secure a majority of delegates to the Democratic National Convention. His only shot at the presidency is to receive enough delegates to force a brokered convention by denying either Clinton or Obama a majority, and then to emerge as the compromise candidate among the national convention delegates in Denver in August. Needless to say, this is a very long shot, and it isn't clear if he will, as a result, drop out of the race, or will stay in until the Convention.
Clinton and Obama, of course, have vigorous campaigns with a real shot of winning a majority of the delegates at this point, although Clinton is the leader in both national polling and state by state polling aggregated into national totals, at this time.
Kucinich supporters, who make up as much as 4% of the likely primary voter/caucus attendees in some places are probably the least likely to offer their support to Clinton now that Kucinich is out. Obama, Edwards and Gravel will also probably benefit to some extent from Kucinich's withdrawal.