We are three states in, and three candidates have each won one race. While Mitt Romney is the only candidate to show any breadth of support, he is also the candidate who won the smallest of the three states.
The next three races are Michigan, Nevada and South Carolina. Michigan is the largest of the three in terms of popluation. Nevada chooses the largest delegation to the convention.
John McCain has the most recent momentum, but is also trailing badly in the delegate count with only half as many delegates as second placed Mike Huckabee. Momentum may also be an overrated factor. The victor in Iowa placed fourth in Wyoming and the victor in Wyoming a disappointing second in New Hampshire.
I would estimate that John McCain's best chance is in Michigan, Mike Huckabee's in South Carolina and Mitt Romney's in Nevada. In these three states it is probably McCain who has the broadest support and he will compete in all three.
If any of these candidates wins two of the three races then that candidate is the immediate favourite with three victories out of six. Arithmetically that would also mean than one candidate would have won no new race and would be looking extremely weak and might even concede.
If each of these three candidates wins a second state the race would seem to be very open. McCain would be able to claim support in swing states, Huckabee in the GOP's southern heartland and Romney would be leading the delegate count and showing demonstrable strength in the increasingly competitive inland western states.
If Fred Thompson - the runner up in Wyoming - wins South Carolina, an incresingly unlikely, but still credible, prospect then the race opens up even more. This scenario could eliminate Huckabee from contention, though it is worth noting that the upcoming Louisiana primary is one where the evangelicals who won Iowa for him are likely to be very influential.
Either of these open scenarios will test Rudy Giuliani's strategy of entering late in a fractured field. As long as the race remains divided his name recognition and financial resources should make him competitive in the big states which vote on 05 February. If the field rapidly coalesces around one other person he will be very vulnerable. On the other hand, the continuing viability of other candidates leaves less room in the market for him. In particular, McCain's national security credentials and appeal to independents overlap with Giuliani's strengths.
Romney too would be a formidable opponent for Giuliani, as he is the only candidate who can match Giuliani's resources and campaign infrastructure. When the field does narrow, Giuliani would prefer to be facing Huckabee, who has neither McCain's name recognition nor Romney's organisational strength. There are many Republicans who are committed opponents of Giuliani, because of his liberal views on some social questions, but there are at least as many who loathe Huckabee's record of liberalism on taxes and his serious ethical problems.
One thing we can say for certain - the fat lady ain't singing yet.