That's kind of a strange standard -- vote by land masses rather than by voters. It may give desireable results, but it can't be justified nowadays.
It's pretty clear though, that the Lincoln vote in 1860 came from more than 5% of the country's land mass, if we go by counties. The Republicans did very well in Northern farming areas.
But will that really happen this year? For the Democrat to win, he'd probably have to win some rural counties from the Republicans, as Clinton did, and that makes the map look different than it did for Kerry or even Gore.
Also, I'd want to know whether you're concerned about tyranny of the majority in all cases, or only when you're in the minority.