Many upcoming primaries are open to members of all parties.
That favors McCain. For anyone doing the political math, Michael Martin is the unknown variable. The bespectacled computer salesman is a Democrat, but come Tuesday, he might just vote for Arizona Sen. John McCain in Michigan's Republican presidential primary. Considering that 10 of the 17 states holding GOP primaries between now and March 7 allow crossover voters, such voters will play a major role in determining the Republican nominee. If they turn out in big numbers, they will help McCain stay competitive, and perhaps even win.