Thu Jul 24, 2008 12:33pm EDT

By Tim Gaynor

PHOENIX (Reuters) - Two-thirds of U.S. Hispanic voters support Democrat Barack Obama for president over Republican John McCain and the partisan gap among the United States' fastest growing voter bloc is broader than at any point this decade, a study found.

The nationwide telephone survey by the Pew Hispanic Center released on Thursday said 66 percent of a sample of 2,015 registered Latino voters polled said they backed Obama, with 23 percent supporting McCain, a senator from Arizona.

The survey said Obama's strong showing represented a sharp reversal in his fortunes from the primaries "when he lost the Latino vote to Hillary Rodham Clinton by a nearly 2-to-1 ratio, giving rise to speculation in some quarters that Hispanics were disinclined to vote for a black candidate."

The study said 65 percent of Latino registered voters now identified with, or leaned toward, the Democratic Party, compared with just 26 percent who said they identified with the Republican Party.

"This 39 percentage point Democratic Party identification edge is larger than it has been at any time this decade," the study said.

In 2004, President George W. Bush won about 40 percent of the Hispanic vote -- a Republican record -- when he beat Democrat John Kerry. Since then opinion polls showed Republican standing among Latinos had been hurt by a national debate on immigration reform.

The study found 32 percent of respondents said being black would help Obama, an Illinois senator, with Latino voters, while 11 percent said it would hurt. The majority, 53 percent, said his race would make no difference to Latino voters.

Hispanics, who comprise 15 percent of the U.S. population and 9 percent of the electorate, could be a critical swing voting bloc in battleground states in the U.S. Southwest, as well as in Florida.

In recent weeks both McCain and Obama have addressed several national Hispanic organizations in their hunt for votes, stressing economic and educational proposals they said would help Latinos as well as reviving plans for a comprehensive overhaul of immigration laws.

The study found that 93 percent of respondents said family and pocketbook issues such as education were the most important to them, topping immigration, which was a priority for 75 percent.

More than three quarters of Hispanic registered voters, or 76 percent of the total, said they had a favorable opinion of Obama. By contrast, 44 percent of Hispanics have a favorable opinion of McCain, and 27 percent have a favorable opinion of Bush.

A drive by Hispanic activists is seeking to get 2 million new voters registered before the election in November.

The survey was conducted between June 9 and July 13 by telephone and had a margin of error of 2.8 percentage points.

(Reporting by Tim Gaynor; Editing by David Wiessler)