Washington ? Minority Americans have been flocking to the nation’s “swing counties,” hotly contested areas that could play a crucial role in this year’s election.

That’s got to be good news for Barack Obama, bidding to become the first black president.

Blacks and Hispanics are moving to counties that already were racially diverse, such as Osceola in central Florida and Mecklenberg in North Carolina, home to Charlotte. They also are moving to key counties that remain predominantly white, such as Lake in Northeast Ohio, Lehigh in eastern Pennsylvania and Oakland outside Detroit.

If this year’s election is as close as the past two, demographic shifts in these counties could make a big difference.

National changes

The racial changes reflect national trends: 93 percent of all counties are less white than they were at the start of the decade, according to new Census estimates. But the changes are even more profound in swing counties of potential battleground states, counties that were decided by razor-thin margins in 2000 and 2004 and could decide statewide winners this year.

“The key this time is there are a fair number of battleground states that are becoming more diverse, and maybe diverse enough to make a difference,” said William Frey, a demographer at the Brookings Institution, a Washington think tank.

“The diversity used to be mainly in pretty safe states, like Texas, California and New York,” he said.

Minorities increasing

The Census Bureau last week released 2007 data on race, age and Hispanic origin for all 3,141 counties in the nation. The Associated Press used the data to analyze 129 key counties in 14 states expected to be the most competitive in this year’s presidential election. Each county was decided by no more than 5 percentage points in the past two elections, and each sits in a state that could go either way this year.

The analysis showed that from 2000 to 2007, minorities made up a growing share of the population in all but 12 of the swing counties. The changes happened among every age group, even seniors, though they were much more pronounced among the young, including those too young to vote.

Obama, who had a white mother and black father, overwhelmingly won the black vote in the Democratic primaries, and he is polling more strongly than Republican John McCain among Hispanics.

Obama also has a big lead among voters younger than 34, according to a recent AP-Ipsos poll. But while young voters have increased their turnout in recent elections, they are still less likely to vote than any other age group.

Obama “may be generating excitement,” said Vincent Hutchings, associate professor of political science at the University of Michigan. “But is he generating enough enthusiasm to excite people who lack a formal education and are disproportionately young, and not likely to vote?”

Hutchings said the demographic changes could affect this year’s election, but he expects the impact to be greater in future elections as young minorities, particularly the booming Hispanic population, become older and more politically active.

More diverse

The Census numbers are based on estimates, and in some counties changes in racial composition are small enough to be statistically insignificant. But the trend is clear: The nation is becoming increasingly diverse, even more so in areas that have been decisive the past two presidential elections.

The AP analysis looked at counties in Colorado, Florida, Georgia, Indiana, Iowa, Michigan, Missouri, North Carolina, New Hampshire, New Mexico, Ohio, Pennsylvania, Virginia and Wisconsin. Nevada also was analyzed because it is a competitive state this year. None of the state’s counties met the criteria for swing counties in the previous two elections, but each has become more diverse since the decade began.

Some states are more competitive than others, and many of the counties remained overwhelmingly white. But given the closeness of the past two presidential elections, even small changes could make a difference in competitive states.