At Facing South, we've provided you with extensive coverage of how the elections are playing out in three key battleground states: Florida, North Carolina and Virginia.

Over the last two weeks, each has become an even bigger battleground -- and are increasingly viewed by both campaigns as being decisive to the outcome of the presidential race. Why is that?

Size matters.

First, the polls. Thanks to a surge by Sen. Obama over the last two weeks, all three states are now listed as "toss-ups" by Pollster and RealClearPolitics. The Atlantic Monthly calls NC and VA "true toss-ups," and FL a "marginal toss-up." Even Karl Rove is saying all three are too close to call [pdf].

But that's not the only reason McCain and Obama are pouring resources into all three Southern states. Close polls are only half the equation; the other half is the payoff if you win.

Here's what I mean. Depending on the overall state of the race, investing in a state where you have a great chance to win but it only nets you 10 Electoral College votes, may not be as good as investing in a state that's a longer shot but the payoff is 20 EC votes.

It's on the second half of the equation that the importance of Southern states emerge. Each are especially prized targets because of their Electoral College vote share. Florida has more Electoral College votes (27) than any other swing state in the country. After Ohio and Pennsylvania, North Carolina and Virginia are the next two biggest swing-states with 15 and 13 EC votes, respectively.

You can see the importance of payoff at Nate Silver's 538.com. Silver has given each state "Tipping Point" rankings, meaning the number of times in simulated races that they prove decisive to the outcome.

As Florida, North Carolina and Virginia have grown tighter in the polls, their large Electoral College vote share has moved them quickly up Silver's tipping point rankings:

TOP 10 "TIPPING POINT" STATES FOR 2008

1. Ohio
2. Pennsylvania
3. Virginia
4. Florida

5. Michigan
6. Colorado
7. North Carolina
8. Indiana
9. Missouri
10. Minnesota

The South's political clout will only grow in future elections as it continues to rapidly grow in size; Southern states will gain as many as nine Electoral College votes after the 2010 Census. But as Silver shows -- and both McCain and Obama know -- the South's clout is already clear.