OMAHA, Neb. | As a rule, presidential candidates haven't had to stump in Nebraska for decades.

That's because this Republican stronghold has given its five electoral votes to the GOP candidate in every presidential election since 1964.

But Barack Obama has opened an office here, trying to take just one of those five votes this year by focusing on Omaha, the state's biggest, most diverse city.

"If the major competitive states are split, we could be talking about a situation where one electoral vote matters," said Randall Adkins, a political science professor at the University of Nebraska at Omaha.

It's a scenario that's only possible in Nebraska and Maine, because they're the only states that can split their electoral votes, although it's never happened.

Here's how the math could work on Nov. 4, according to Nebraska Democrats:

Obama and Republican John McCain each take most of the states they're expected to win, based on past election history and polling.

But Iowa, Nevada and New Mexico change from the Republican to the Democratic column, and — by the Democrats' math — the electoral vote ends up tied at 269.

That is, unless one of Nebraska's five votes goes to Obama and carries him into the Oval Office.

Political observers acknowledge the race could be close.

The Obama campaign started canvassing Omaha neighborhoods last month, and John Berge was hired as director of Obama's Nebraska campaign. He said that while some resources will go into the rest of the state, they'll be focused on the 2nd District.

For several reasons:

Omaha is the largest city in the state by some 175,000 people, and gives Obama a small geographic area to focus on.

Also, television ads are already running here. Omaha and Council Bluffs, Iowa, are just across the river from each other. In buying television ads to reach the Council Bluffs audience, a campaign sees a lot of spillover onto Omaha networks.

Omaha also has most of the state's black population and much of the state's population of Hispanics and other minorities. Polls show that, nationally, those groups heavily favor Obama.

Still, Adkins isn't convinced Obama can actually win the electoral vote. Republicans have a 15,000-voter advantage in the district — much less than in other parts of the state, but still formidable.

But the attention is unprecedented, Adkins said, and while McCain may struggle to afford campaigning in states such as Nebraska, he can't afford not to.

McCain's going to have to respond in Nebraska, Adkins said.

"How much he has to respond is really going to be a strategic decision of the campaign," Adkins said.

So far, McCain's effort in the state is largely volunteer.

The Nebraska Republican Party is canvassing on his behalf, said executive director Matt Miltenberger. Volunteers are hitting thousands of households with information about McCain and state candidates, Miltenberger said.

McCain was in Nebraska for a high-dollar fundraiser in July. Obama hasn't been back since he visited Omaha in February for an appearance days before the state's first-ever Democratic caucus, which he won handily.

Loree Bykerk, chairwoman of the political science department at UNO, said some of the attention for Nebraska might be less about how good a chance Obama has at getting the electoral vote, and more a result of Obama "having more money that he knows what to do with."

But "if they're going through the trouble of setting up campaign offices in Nebraska, Alaska, Wyoming, maybe it is going to be close," Bykerk said. "I would give a lot of credit to their behavior."

As for what that means for the average Nebraskan, Berge of Obama's Nebraska campaign sums it up: "They're going to be hearing from us."

By ANNA JO BRATTONAssociated Press WriterOn the Net:

Obama campaign: http://www.barackobama.com

McCain campaign: http://www.johnmccain.com

Copyright 2008 The Associated Press.