Republicans rule rural areas, while any Democrat can count on running up big margins in most of the large cities in the country. That has left the suburbs as the main partisan battleground.
For several election cycles now, the presidency has been won or lost based on the vote among suburbanites in a few key states. That's likely to be true again this November.
And some political observers believe that President Obama took the calculated risk that his newfound support for gay marriage rights will boost his campaign in these all-important counties.
Suburbanites tend to be liberal to moderate on social issues. Obama's stance in favor of same-sex marriage, combined with Republican attacks on birth control and abortion, could hurt all-but-official GOP nominee Mitt Romney among suburbanites, some observers say.
"Gay marriage is more dangerous in moderate swing suburban communities for the Republicans than it is for the Democrats," says Lawrence Levy, executive dean of the National Center for Suburban Studies at Hofstra University. "The mistake Republicans have made with suburban voters is expecting that they're like Republicans in red communities."
As the nation's older, inner-ring suburbs have grown denser and more diverse, they have also become more Democratic. Large counties that used to be favorable territory for Republicans — such as Fairfax County, Va., outside Washington, D.C., and Nassau County, N.Y., on Long Island — are now rich sources of Democratic votes.
Obama's victory in 2008 came about partly thanks to his ability to dominate larger suburban counties in states such as Colorado, Ohio and Pennsylvania. And he became the first Democrat to carry Virginia since 1964 by running up good-sized margins in the populous suburbs outside Washington, D.C.
But while Levy expects Obama's support for gay marriage to play well in many suburban areas, he doesn't expect it to override other issues of primary concern — most notably, the economy.
"This issue, for most suburban voters, is going to be way, way, way down the list of priorities," says Whit Ayres, a Republican political consultant. "Suburban voters are going to be voting overwhelmingly on the economy, jobs, spending and debt."
The gay-marriage issue, meanwhile, is likely to help Romney among rural and religious voters — strongly Republican constituencies that have been less than wildly enthusiastic about his campaign.
"The one negative consequence of this for Obama is that this could increase energy and support from the core groups that Romney needs for election," says Frank Newport, editor-in-chief at Gallup, the polling organization.
Denser And Democratic
Even in North Carolina, where voters overwhelmingly approved a ban on gay marriage Tuesday, several of the state's most populous counties, such as Wake, Mecklenburg and Durham, voted against the ban.
"I think the White House looked at that vote and decided it was a finally safe to go out into the water," says Henry Olsen, vice president of the American Enterprise Institute, a conservative think tank. "This is potentially a wedge issue among moderate suburbanites nationwide."
Recent polling by the Pew Research Center shows that residents of the suburbs support gay marriage, though not overwhelmingly so. Forty-eight percent of suburbanites are in favor of gay marriage, compared with 41 percent who are opposed. By comparison, 53 percent of rural Americans are opposed to gay marriage, and 36 percent in favor of its legality.
"Even if you can make the case that suburbanites live in the most segregated places, they are turned off by any overt display of bias," says Levy, the Hofstra scholar. "That doesn't fit their image of themselves."
Still, when asked about the salience of same-sex marriage, suburbanites — like just about everyone else — rank it pretty low on the list.
Ayres, the GOP consultant, suggests that gay marriage, like student loans, represents an attempt by the White House to appeal directly to particular constituencies.
Gays make up a crucial share of Obama's top campaign donors. Since the president announced his support for gay marriage on Wednesday, social media sites have been buzzing with gays and others announcing fresh campaign donations.
Many have posted, for instance, about their decision to give $1 to Obama's campaign for every year of a committed relationship — their own or a loved one's.
"Politically, this looks like a concerted strategy by the president and his team to gin up support among elements of his coalition that are not particularly energized about his campaign," Ayres says. "He's doing it because he's losing independents left and right because of the lousy economy and his handling of it."
The Battle Out West
In Colorado — widely considered one of the main battleground states this year — voters six years ago approved a ban on gay marriage. In 1992, they voted to block the state and municipalities from affording gays basic rights in areas such as housing and employment — a measure that was later overturned by the U.S. Supreme Court.
But support for gay marriage has grown in Colorado, as elsewhere, and is now a "50-50" proposition in the state, says Denver-based pollster Floyd Ciruli. "Like the nation, we have evolved," he says.
Colorado's regular legislative session ended Tuesday with a bill to allow gays to enter into civil unions blocked through procedural maneuvers. But Democratic Gov. John Hickenlooper has called a special session, starting Monday, to deal with civil unions and other matters.
"I consciously try to avoid divisive issues that are intensely polarizing," Hickenlooper said Thursday. "That being said, when it comes down to civil rights, you don't really have a choice."
Ciruli predicts that Republicans will have a hard time using the issue effectively against Democrats in the Denver suburbs, saying the issue lacks the sort of "bite" it once had.
On the other hand, he doesn't expect gay marriage to be a big political winner for Obama or other Democrats, either.
"In the suburbs, unless you are really into gay rights, this doesn't seem like one of the biggest issues," Ciruli says. "We're so utterly consumed by the economy."