The 2008 US presidential election will most likely end in the following manner:
The Democratic party will nominate Hilary Clinton for President, and, Obama, for VP. if this sequence fails, then, it will be reversed. That is, Obama for President and Clinton for VP.
That makes for a very powerful ticket for the Republicans to beat. The appeal of this ticket would capture a majority of American votes (women, men, blacks, hispanic). I really cannot see John Edwards making it to the end.
For the Republicans, it is more complicated are harder to predict. There is no one strong contender at this point. I want to say John McCain, but his strength is debatable. Huckabee is likeable, kinda a down-home guy, but like all the Republican candidates, his strength is debateful.
Would a McCain- Romney defeat a Clinton-Obama ticket? I doubt it. How about a McCain - Huckabee? I doubt it. How about Romney - Huckabee? Some think that is a strong ticket. Let's not even discuss Thompson, he will be out by August.
So, the Republicans lack the passion, lack the ability to excite the voter. They are basically boring. The Democrats clearly have the edge here and I see no way that will diminish. I think the Democrats will win in November.. unless... world events and the US economy make the Republicans look attractive.