Today the AFL-CIO is scheduled to officially endorse Sen. Barak Obama for president.

The AFL-CIO’s endorsement will unite all of labor’s support behind Sen. Obama. The group of unions that left the AFL-CIO three years ago, known as the Change to Win federation, endorsed the Illinois senator in late February. Unions across the labor movement have said they will spend a record $300 million to help elect Democrats to the White House and Congress this fall.

Unions are expected to focus on shoring up support for Sen. Obama among white working-class voters. “Organized labor can play an important role to bring those voters over to Barack Obama, and that could be decisive,” said Peter Francia, a professor of political science at East Carolina University.

Labor’s support for Sen. Obama has evolved significantly over the past six months, tracking the arc of his campaign. Sen. Hillary Clinton won early support from influential labor leaders, partly as a result of longtime ties to them. Former North Carolina Sen. John Edwards also initially attracted more labor backers than Sen. Obama. Some union officials were unsure at the outset about Sen. Obama’s stands on labor’s legislative priorities, from union organizing to trade.

The AFL-CIO hopes to influence numerous races in the 2008 election, from state battles to the presidential race. It says it will deploy 250,000 volunteers to reach out to 13 million voters in 23 priority states, with a focus on Ohio, Pennsylvania, Michigan, Wisconsin and Minnesota, where union membership rates are among the highest in the country. It expects one in four voters in November to come from a household where at least one person is a union member.

This could give Obama a needed boost in the “Rust Belt” where he did pitifully in the primaries.  He will need support from white, working class voters if he is to win in November.  But will this endorsement and promise of assistance put him in the White house.  That is the question.