"We're proud to stand with Senator Obama to help our nation chart a course that will improve life for generations of working people and our children," said AFL-CIO President John Sweeney.
Union support is key for Democratic candidates because of labor's deep pockets and its ability to turn out union voters.
Between the AFL-CIO and its chief rival, the Change to Win labor organization, the nation's labor movement plans to spend around $300 million on the 2008 elections. Change to Win, made up of seven powerful unions that broke away from the AFL-CIO in 2005, already has endorsed Obama. The AFL-CIO represents 9 million union members; Change to Win, 6 million.
The AFL-CIO says one in every four voters going to the polls on Nov. 4 will be a union household voter, and its planned campaigns will reach more than 13 million people, including in key states like Ohio, Pennsylvania, Michigan, Wisconsin and Minnesota.
"We want to engage our members and all working people on the need for action on the issues that make a difference in our daily lives," said Ed Hill, president of the International Brotherhood of Electrical Workers.
Labor unions are also reliable Democratic donors.
In the 2004 elections, organized labor gave $53.6 million to Democratic candidates and party committees in a losing effort to capture both the White House and Congress, according to the Center for Responsive Politics. That number rose to $57.5 million in 2006, when Democrats successfully took the House and Senate from the GOP.
The AFL-CIO endorsement has been expected since Obama's main Democratic primary rival, Sen. Hillary Rodham Clinton of New York, dropped out of the race and endorsed Obama. The AFL-CIO stayed neutral but allowed its unions to endorse individually during the primary. A dozen of its unions supported Clinton.
Gerald McEntee, president of the American Federation of State, County and Municipal Employees, was one of Clinton's top union supporters and is also the AFL-CIO's political committee chair.
"We'll work our hearts out for Barack Obama," McEntee said. "Our program is going to be worker to worker and neighbor to neighbor. We're ready to mobilize. We're ready to rock and roll. This country and our people are ready for change."
Obama met personally with AFL-CIO leaders at their Washington headquarters last week, receiving an enthusiastic reception from the top unions.
The AFL-CIO already has been campaigning against Republican nominee-in-waiting John McCain, but now will start promoting Obama's candidacy to its members and their families and friends.
The Republican National Committee said the endorsement contradicts Obama's stated objections to special interests.
"Obama is putting his own political interests first, accepting the sort of support he used to rail against," said RNC spokesman Alex Conant.
The AFL-CIO's general board, which made the endorsement decision, noted that Obama has voted with the labor movement 98 percent of the time while McCain voted with them 16 percent of the time.
"Of the two candidates for president, there is no comparison," the endorsement announcement said. "Senator Obama deserves our full, united and unwavering support."
The AFL-CIO will spend the next couple of months introducing Obama to its members, said Karen Ackerman, the AFL-CIO's political director. After that, it will turns its attention to get-out-the-vote efforts, she said.
