This is another great strategic move by the republican party. Let the two democrats fight against each other all they can, while taking focus of John McCain.
Then when the real election cycle begins, they can put credibility behind a claim that the democratic candidates are focusing more on getting elected than the real issues, and they dont have a clear focus on solving the problems that the United States faces.
It will be another smear fight, and unfortunally I think the average voting american will think “well, they fought each other, instead of solving their differences, ill vote McCain”, which is going to put the US further down the drain.
You gotta give some credit to the strategists in the republican party, Carl Rove is a mastermind in this game, even though he is pure evil.