The longstanding gap between blacks and whites in voter participation evaporated in the presidential election last year, according to an analysis released Thursday. Black, Hispanic and Asian voters made up nearly a quarter of the electorate, setting a record.

The analysis, by the Pew Research Center, also found that for the first time, black women turned out at a higher rate than any other racial, ethnic and gender group.

The study attributed the findings to several factors beyond the obvious one: Barack Obama’s candidacy. For instance, the number of eligible Hispanic voters has soared by more than 21 percent since 2004, a reflection of population gains and growing numbers of Hispanics who are citizens. Their share of eligible voters increased to 9.5 percent, from 8.2 percent four years earlier. In 2008, for the first time, the share of white non-Hispanic eligible voters fell below 75 percent.

“What this report demonstrates is a pretty potent one-two punch of demographic change and behavioral change,” said Paul Taylor, executive vice president of the Pew Research Center. “The white share of the overall vote has been stepping down pretty steadily for 20 years.”