WASHINGTON (AP) – Blacks voted at a higher rate than other minority groups in 2012 and, by most measures, surpassed white turnout for the first time, reflecting a deeply polarized presidential election in which blacks strongly supported Barack Obama while many whites stayed home.

Had people voted last November at the same rates they did in 2004, when black turnout was below its current historic levels, Republican Mitt Romney would have won narrowly, according to an analysis conducted for The Associated Press.

Census data and exit polling show that whites and blacks will remain the two largest racial groups of eligible voters for the next decade.

Last year’s heavy black turnout came despite concerns about the effect of new voter-identification laws on minority voting, outweighed by the desire to re-elect the first black president.

Blacks formed long lines and in some cases waited for hours to cast their ballots.

One woman who did not let age or long lines prevent her from voting was invited to President Barack Obama’s inauguration address in January.

Tipping point

William H. Frey, a demographer at the Brookings Institution, analyzed the 2012 elections for the AP using census data on eligible voters and turnout, along with November’s exit polling. He estimated total votes for Obama and Romney under a scenario where 2012 turnout rates for all racial groups matched those in 2004.

Overall, 2012 voter turnout was roughly 58 percent, down from 62 percent in 2008 and 60 percent in 2004.

The analysis also used population projections to estimate the shares of eligible voters by race group through 2030. The numbers are supplemented with material from the Pew Research Center and George Mason University associate professor Michael McDonald, a leader in the field of voter turnout who separately reviewed aggregate turnout levels across states, as well as AP interviews with the Census Bureau and other experts.

Overall, the findings represent a tipping point for blacks, who, for much of America’s history, were disenfranchised and then effectively barred from voting until passage of the Voting Rights Act in 1965.

Cautionary note

But the numbers also offer a cautionary note to both Democrats and Republicans after Obama won in November with a historically low percentage of white supporters. While Latinos are now the biggest driver of U.S. population growth, they still trail whites and blacks in turnout and electoral share, because many of the Hispanics in the country are children or non-citizens.

In recent weeks, Republican leaders have urged a “year-round effort” to engage black and other minority voters, describing a grim future if their party does not expand its core support beyond white males.

The 2012 data suggest Romney was a particularly weak GOP candidate, unable to motivate white voters, let alone attract significant black or Latino support. Obama’s personal appeal and the slowly improving economy helped overcome doubts and spur record levels of minority voters in a way that may not be easily replicated for Democrats soon.

Romney would have erased Obama’s nearly five million vote victory margin and narrowly won the popular vote if voters had turned out as they did in 2004, according to Frey’s analysis. In that election, white turnout was slightly higher and black voting lower.

Obama effect

More significantly, the battleground states of Ohio, Pennsylvania, Virginia, Florida and Colorado would have tipped in favor of Romney, handing him the presidency if the outcome of other states remained the same.

“The 2012 turnout is a milestone for blacks and a huge potential turning point,” said Andra Gillespie, a political science professor at Emory University who has written extensively on black politicians.

“What it suggests is that there is an ‘Obama effect’ where people were motivated to support Barack Obama. But it also means that black turnout may not always be higher if future races aren’t as salient.”