By Deborah Quinn Hensel

HOUSTON (Reuters) - Vice President Joe Biden drew cheers from the nation's biggest civil rights group on Thursday with a fiery defense of President Barack Obama's record, and he warned that the election of Republican Mitt Romney could reverse years of economic and civil rights gains for blacks.

The day after Romney was booed during an appearance before the National Association for the Advancement of Colored People convention, Biden said Republicans had blocked Obama's efforts at every turn and their policies would halt progress for blacks in housing, education and a variety of economic issues.

"Their discipline has been amazing. They have never let up. But neither has my guy, Barack Obama," Biden said. "This election, in my view, is a fight for the heart and soul of America. These guys aren't bad guys, but they have a fundamentally different view."

It was a rousing speech to a friendly crowd by Biden, who has proved to be a passionate campaigner for Obama, drawing on his folksy charm and connection with working-class America.

Biden asked the audience to imagine what a Romney presidency would mean for the Justice Department, the Supreme Court and voting rights.

"This is not your father's Republican Party," said Biden, the former chairman of the Senate Judiciary Committee. "They see a future where voting is made harder, not easier."

He condemned Republican support for voter ID laws that critics say will disenfranchise many black voters.

"Did you think we'd be fighting these battles again?" he asked the crowd, which roared "No!" in reply.

"When you have the right to vote, you have the right to change things," he said. "We see a future where those rights are expanded, where access to the ballot is unencumbered."

His message resonated with the audience in Texas where a new voter ID law has angered black activists who say it would deny hundreds of thousands of people access to voting. The law is being challenged in a federal court in Washington this week.

Romney drew boos from the NAACP audience on Wednesday for blasting Obama's healthcare overhaul and his leadership on the economy. Romney promised to improve life for blacks by turning around the economy and cutting unemployment - at 14.4 percent for blacks compared to the national average of 8.2 percent.

TOUGH DECISIONS

Biden said Obama had made the tough decisions that pulled the economy out of recession with his economic stimulus plan and auto industry bailout, despite repeated opposition from Republicans in Congress.

He predicted the election would turn on character and vision, and "it will not surprise you - I don't think it's even a close call," he said.

Blacks are the most reliable Democratic voting bloc, and more than 95 percent backed Obama in 2008. Polls show Obama, the first black U.S. president, has similar levels of support among African Americans this year four months before the November 6 election.

Voter turnout among blacks in November could be crucial, however. National opinion polls show a tight race between Romney and Obama, with many polls giving Obama a slight lead.

Biden was appearing at the convention for Obama, who sent a brief, taped video message telling the group, "I stand on your shoulders."

The mostly black crowd frequently roared its approval for Biden and shouted in dismay when he indicated he was wrapping up his speech.

"I think it was a clear indication of the intent of the administration to continue to be sure that everyone is treated fairly and equally, and that we try to generate more jobs and strengthen the economy," said James Gallman, a retired educator from Aiken, South Carolina, who serves on the NAACP board.

(Writing by John Whitesides; Editing by Alistair Bell and Cynthia Osterman)