The nation's inner suburbs, including those around Washington, face critical challenges from aging neighborhoods and growing numbers of poor, elderly and immigrant residents, according to a report to be released today. In some cases, it says, the fate of those communities could undermine their regions.

Washington's suburbs are dealing with those issues better than most, said researchers at the Brookings Institution, citing Arlington County's policy of promoting dense development near Metro stops as a national model for how to stay vibrant.

The nation's "first suburbs," which began drawing people out of big cities in large numbers half a century ago, now have deteriorating roads, commercial strips and housing. Those problems, coupled with demographic changes, mean that the communities "are staring down a looming set of challenges that threaten their overall stability," according to the report.

The population in these close-in communities has grown steadily and still outnumbers residents in the exploding outer suburbs and central cities they border. But despite their numbers, they fall into a "policy blindspot" because government programs focus more on building roads in the exurbs or fighting blight in central cities, the Brookings report says.

Once less diverse than the nation as a whole, the inner suburbs are now more so, a change accompanied by income and education disparities they are struggling to address. Nationally, one in three residents in the inner suburbs is a member of a minority group, compared with one in six in 1980. In the Washington area, the figures are higher, ranging up to 76 percent in Prince George's County.

"The health and vitality of these places is really central to the health and vitality of the metropolitan areas in which they are located," said Bruce Katz, director of the metropolitan policy program at the Brookings Institution.

Montgomery County Executive Douglas M. Duncan (D) said he pushed the revival of downtown Silver Spring because "the fear was, if we don't stop the blight in Silver Spring, it's just going to creep up Georgia Avenue into Wheaton, Olney -- and the eastern third of our county would be blighted, and what would we do then?" Duncan said the challenge of the inner suburbs "is they very quickly become part of the center city."

In their favor, some "first suburbs," including those around Washington, are home to better educated and more affluent residents than cities or exurbs. 

Unlike suburban Chicago, where dozens of small municipal governments compete with each other, such inner counties as Montgomery and Prince George's are large enough to command attention from state legislatures. In fact, the Brookings report says, half of Maryland residents live in older first suburbs.

Older suburbs are also reshaping their political identity, according to another report, from the Metropolitan Institute at Virginia Tech, also to be released today. They are giving a growing share of their votes to Democrats, the report says, and politically have more in common with neighboring big cities than with suburbs farther out.

The Metropolitan Institute report says that inner suburbs of the nation's 50 biggest metropolitan areas increasingly trend Democratic. They voted for Democratic presidential candidates John Kerry in 2004 and Al Gore in 2000 but gave Kerry a bigger margin. As Republicans stake claim to votes in outer suburbs, smaller metropolitan areas and rural America, these older, urbanized communities offer new opportunities to Democrats, the report says.

Fairfax County, for example, which includes communities inside the Beltway, voted for the Democratic presidential candidate in 2004, the first time it has done so in 40 years.

"The old division of city and suburbs doesn't hold up anymore," said Robert E. Lang, director of the institute. Now, "the more important divide is older and newer suburb."

The exurban issues in Loudoun and Charles counties stem from crowded schools, congested roads and other growing pains. People in older communities want help in upgrading aging facilities and providing social services, but the Brookings report says they often find that programs are targeted more at inner cities.

In Prince George's, crime and deteriorating housing are long-standing problems for some inner communities, but other parts of the county are attracting upscale development. For many residents there, "the older communities serve as the affordable housing stock," said County Council member David Harrington (D-Cheverly), who is concerned that rising real estate values could make it hard for longtime owners to be able to pay property taxes.

Brookings researcher Robert Puentes pointed to Arlington's success in concentrating development to build tax revenue and reduce road congestion while protecting some residential neighborhoods. But the county also faces an affordable housing crunch and the same demographic challenges as other older communities.

Evelyn Flax, 85, a retired federal employee, has lived in the county since 1974. But when her rent began rising beyond what she could afford, she moved into Culpepper Garden, a nonprofit home for low-income seniors. The building offers services that include a shuttle bus to the grocery store, but she prefers to walk.

"I'm not ready for that," she said. "I need the exercise."

Arlington's population of people 85 and older has nearly doubled in the past two decades, county officials say. A growing number are low-income, but the county retains its image as an affluent community.

"The people in Richmond say, 'We don't think of Northern Virginia as a place for poor people,' " said Terri Lynch, director of the county's agency on aging. "We have people who can afford, and we have bunches of people who can't."