The battle for the White House is still in its early, often silly stages - a time when issues such as the economy and national security can be overshadowed by spats over which candidate would be better for dogs.
But in the end, the Nov. 6 election between Democratic President Barack Obama and presumed Republican nominee Mitt Romney will hinge on 10 politically divided states, nine of which Obama won when he defeated Republican John McCain in 2008.
The states range from former Republican strongholds such as North Carolina and Virginia to a few key battlegrounds - namely Ohio, Florida and Nevada - where a sputtering economy gives Romney a chance to break through. Pennsylvania, Colorado, Iowa, Arizona and New Hampshire also are up for grabs.
Obama dramatically expanded the political playing field for Democrats in 2008 by winning states such as Indiana that had not backed a Democratic presidential contender in a generation.
In this year's state-by-state race for the 270 electoral votes needed to win the election, Obama is the early favorite in states that would give him 227 electoral votes. Romney leads in states that would give him 180.
That gives Obama larger room for error than Romney as the two wrestle for the 131 electoral votes at stake in the toss-up or "swing" states.
A state's electoral votes reflect its number of seats in Congress, most of which are based on population.
Larger states such as California (which has 55 electoral votes and likely will go for Obama) and Texas (which has 38 and is likely to back Romney) can be windfalls, but in close elections, narrowly divided states such as Ohio (18 votes) typically determine the outcome. All of the states except Maine and Nebraska award all of their electoral votes to the candidate who carries the state.
When Obama rolled up 365 electoral votes and nearly 53 percent of the popular vote to defeat McCain in 2008, Obama's personal ratings were strong and he did not have much of a record on spending, deficits and healthcare for foes to target.
But jobless rates above 8 percent, and public doubts about Obama's leadership on the economy and his landmark healthcare overhaul have helped push his approval ratings below 50 percent since then. That has put him at risk in several of the key states he won in 2008.
"Obama will be playing defense, but he has some ground that he can give up and still win," said Bruce Haynes of Purple Strategies, a bipartisan consulting firm that is conducting monthly opinion polls in swing states.
"To some extent, he's running a national triage operation, and he just can't lose too many patients," Haynes said. "He can lose a few states from 2008, but he has to have some firewalls."
OBAMA'S PATHS TO VICTORY
Both Obama and Romney head into the campaign with a solid base of states where they can expect easy wins.
Obama is likely to carry the West Coast and most New England and Northeastern states, while Romney will be heavily favored to sweep most states in the South and Great Plains.
Obama must defend seven states he won in 2008 by fewer than 10 percentage points -- Colorado, Ohio, Indiana, New Hampshire, Virginia, North Carolina and Florida.
Romney is an early favorite to reclaim traditionally Republican Indiana. But to deny Obama a second term, he also needs a combination of victories in the fiercely contested swing states of Ohio and Florida, historically conservative North Carolina and Virginia and in one or two other toss-ups.
Polls show close races in all of the key battlegrounds, although Obama has slight leads in Ohio and Florida, the cornerstones of any Romney victory scenario.
The Obama campaign promises to compete in all of the states it won in 2008, and hopes to get a boost in the southwestern state of Arizona with the help of the state's growing Hispanic population, whose support has been trending toward Democrats.
The candidates' recent campaign schedules are signaling which states they see as crucial.
Obama traveled to New Hampshire, Colorado and Iowa last week, and will hold his first formal campaign rallies on Saturday in Ohio and Virginia. Romney, meanwhile recently has been in Ohio, Pennsylvania, Arizona, North Carolina and New Hampshire.
"We have worked hard to expand the map and have many ways to get to 270 electoral votes," Obama campaign manager Jim Messina told reporters in a conference call last week. "We believe there are even more pathways than there were before, but clearly Virginia and Ohio are two critical states in this campaign."
HOW ROMNEY COULD WIN
If Romney can hold all 22 of the states won by McCain in 2008, he could start his path to the White House by reclaiming Indiana and Virginia - which until Obama came along had not backed a Democrat in a presidential race since 1964 - and North Carolina, which had been reliably Republican since 1976.
The traditional battlegrounds of Ohio and Florida, king makers in recent national races, loom again as critical pieces of Romney's electoral puzzle. Florida's hotly disputed results gave Republican George W. Bush the 2000 election, while Democrat John Kerry's upset hopes were dashed when Ohio narrowly backed Bush in 2004.
Both states have been hit hard by economic turmoil under Obama, although Ohio's unemployment rate has recovered to dip slightly below the national average. Florida is one of four battlegrounds, along with Nevada, North Carolina and Arizona, with unemployment rates higher than the national average of 8.2 percent.
Even reclaiming Virginia, North Carolina, Indiana, Ohio and Florida and their combined 86 electoral votes from Obama would leave Romney four electoral votes short of 270, forcing him to take at least one other state from the battleground list.
"It is very difficult to see how Romney can win without taking those five states," Quinnipiac pollster Peter Brown said. And even then, "he still needs one more."
Republican strategist Todd Harris counters that Obama's record on the economy and as the overseer of a rising federal debt - now at more than $15 trillion - will complicate the president's re-election bid.
"It's going to be a lot tougher for the president this time than in 2008," Harris said. "As hard as the Obama campaign is trying to make this election about Mitt Romney, the fact is this is going to be a referendum on the president's record and the idea of whether people want four more years of the same."
Democrats hope that Republicans' harsh rhetoric on immigration - including Romney's opposition to a bill that would give legal status to children of illegal immigrants who serve in the military or go to college - will accelerate a recent shift of Hispanics toward Democrats. Such a shift could particularly boost Democrats in the western states of Nevada, Colorado, New Mexico and Arizona.
Obama won about two-thirds of Hispanics' votes in 2008, aiding his victory margins in Colorado, New Mexico and Nevada.
Hispanics - who account for 16 percent of the U.S. population and grew 43 percent during the last decade - also could have key roles in Ohio, North Carolina, Florida, Virginia and elsewhere.
"The tone of the immigration debate has been very ugly. It's going to be a challenge for any Republican ... to appeal to Hispanic voters," Democratic strategist Karen Finney said.
Other factors could help Romney in the West. Nevada has been hit hard by a 12 percent state un
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