Younger, Democratic-leaning professionals have flocked to North Carolina's Research Triangle and the northern Virginia suburbs around the nation's capital. Both states also have large minority populations; those groups voted in record numbers for Obama in 2008.
Obama picked Charlotte, N.C., for the Democratic National Convention in September. While convention hosts have been unreliable general election indicators, Obama was the first Democrat to carry Colorado since 1992 after accepting the nomination in Denver. Obama kept thousands of the volunteers he sent out for that convention to work through the election, as he could in North Carolina.
Though defending inroads into Republican states, Obama has an advantage of forcing Romney to spend money there, and that, Obama aides say, shows some of the options of reaching 270.
"We have an ability to win in a number of different scenarios," said Obama's campaign manager, Jim Messina. "The map has moved. This is not your parents' electoral map."
Hispanic voters helped Obama win last time in Colorado, Nevada and New Mexico, and, according to polls, they prefer him over Romney. Romney described GOP primary rivals Rick Perry and Newt Gingrich as soft on illegal immigration, and has said he would veto legislation that would allow certain illegal residents to become U.S. citizens.
But Romney expects to be competitive in all three states. For one, Nevada has a popular Republican governor, Brian Sandoval, who endorsed Romney on Wednesday. Also, unemployment tops 12 percent in Nevada, the heart of the housing crisis.
The Obama campaign is confident it will carry Colorado, where suburban women, a strong suit nationally for the president, in the Denver area are seen as key.
New Mexico has gone back and forth for the past three presidential cycles, and elected a Republican governor in 2010. But the boom in the Hispanic voting population is a challenge for Romney.
"Those Western states are going to depend on the Hispanic turnout and the percentage we get," said Charlie Black, a veteran Republican presidential consultant. "And if we voted today, we wouldn't do well. But we've got plenty of time to work on it."
Iowa, a true swing state over the past three presidential elections, is special to Obama. His upset of Hillary Rodham Clinton in the 2008 caucuses set him on the path to the nomination, and he has kept the fires burning.
Romney waged competitive campaigns for the 2008 and 2012 caucuses, but has struggled to win devotion from conservatives. On Tuesday, he received the endorsement of Gov. Terry Branstad, an economic conservative and establishment GOP figure.
Vice President Joe Biden has campaigned in Iowa twice this year. The Obama campaign included Iowa, along with Colorado, Florida, Nevada, Ohio and Virginia, last week a round of television advertising, highlighting its place as a top target.
Of the GOP states Obama picked off, only Indiana is viewed as uncompetitive in 2012. Obama was the first Democrat to carry Indiana since 1964, and he did so by a single percentage point.
But Obama did win New Hampshire, which flipped from Bush to Kerry in 2004, and is considered a toss-up this year. It's Romney's backyard, where he won the January GOP primary and Republicans have roared back to power in recent years. Biden campaigning in the state Thursday.
Minnesota, Wisconsin, Michigan and Pennsylvania are viewed as competitive, but lean toward Obama's column. Democratic presidential candidates have carried them since at least the 1980s, and earlier.
Romney hopes his native Michigan status and family name — his father was governor in the 1960s — help, as does his business background, given that the state's jobless rate exceeds the national average. But his opposition to the federal auto industry bailout in 2008 may hurt him in the car capital.
Although Romney's national campaign headquarters is in Boston, Republicans say they don't expect Romney to win, and perhaps not compete, in Massachusetts, a traditional Democratic stronghold.
In Wisconsin, conservatives are rallying around Gov. Scott Walker, who faces a June recall election after he signed legislation last year stripping public employee unions of most bargaining power. If Walker prevails, it could embolden Romney.
Bush competed in Minnesota and Pennsylvania in 2000 and 2004, only to have them tip Democrat in the closing weeks. Today, registered Democrats in Pennsylvania outnumber Republicans by nearly 1 million. But a downturn in the economy, or Romney catching fire elsewhere in the nation's economic heartland could tip both Republican.
Obama campaign aides have sent signals they will contest Arizona, arguing the Hispanic voter trend favors them. However, they and Romney aides say that tipping point is years away and that it remains a safe Republican state.
Likewise, Missouri has been decided by slim margins in the past three elections, but carried by Republicans in all three.
As in Arizona and even Georgia, where Obama's team has also made overtures, Missouri is considered GOP territory this year.
"The Romney campaign is going to make sure we have the resources to compete in states where Democrats throw a head fake," Romney's Madden said. "And I'm saying Missouri is not being targeted by the Democrats."
Associated Press writer Ken Thomas in Washington contributed to this report.
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