Unlike the knife-edge contests of 2000 and 2004, this year's presidential election could remake the US political map, and both parties will have to strain every sinew to wage a nationwide battle. The last two elections could have swung either way depending on the distribution of a few thousand votes in a handful of states, and the Democrats and Republicans were able to take support in their strongholds for granted.  But old calculations risk being redundant with the emergence of two contenders, Democrat Barack Obama and Republican John McCain, who bring crossover appeal and are intent on hunting deep in the other's territory. "I don't think the map will look at all the same as last time around," said William Frey, an expert on political demographics at Washington's Brookings Institution, noting that up to 14 states could be in play this year.