The unique analysis from twins Earl and Merle Black points to a recurring battle over the Midwest in presidential campaigns for the foreseeable future. They make their case in a newly published book, Divided America, The Ferocious Power Struggle in American Politics.
Republicans are strong in the South and Mountains/Plains states, and Democrats claim the Northeast and Pacific Coast, but neither can win without reaching beyond their regional strongholds. At the same time, the two parties are getting further apart philosophically.
"American party control could change in every election, and everybody in Congress knows that," said Merle Black, professor of politics and government at Emory University in Atlanta. "It makes it very hard to compromise since each side wants to stand pat until the next election."
Plus, the widening philosophical differences mean anyone approaching the middle ground is seen as weak in the eyes of their base supporters, said Earl Black, political science professor at Rice University in Houston.
"The interesting thing about politics today is nearly everybody is frustrated by the outcome," he said. Losers obviously are unhappy, but winners are as well because they can't pick up enough power to do anything.
So who wins in 2008?
That depends on which party can assemble a ticket that reaches beyond its regional stronghold. Rudy Giuliani running with Fred Thompson could, they say, because a former New York mayor and an ex-senator from Tennessee, both with national names, could break the Democrats' hold on the Northeast and consolidate the South.
"The last thing the Republican Party wants to do is nominate another Southerner. They've maxed out on that," said Merle Black.
Democrats could overcome the regional divide if Hillary Clinton carries Arkansas, Florida and possibly Virginia or Barack Obama's appeal among blacks somehow gives him a few Southern states. One Democrat that could certainly dig into the Republicans' Southern base would be Bill Richardson, they say.
Larry Sabato, political scientist from the University of Virginia and author of Divided States of America: The Slash and Burn Politics of the 2004 Presidential Election, agrees that Mr. Richardson may be the strongest Democrat.
"If the Iraq War is still a disaster in the fall of 2008, any serious Democratic nominee ... may be able to win," Mr. Sabato wrote to an e-mail inquiry. "The GOP candidate will be greatly burdened by Bush and Iraq's unpopularity."
The Blacks contend the regional dynamics could trump all but the most powerful election-year trends. And the regional differences are being reinforced by the way people are moving from region to region, they argue, rather than diluting them with the newcomers' perspectives.
"You can't understand the nation just by looking at national outcomes," said Earl Black. "You have to deconstruct it regionally."