The Service Employees International Union said Tuesday it will target its massive field campaign on turning out voters in just eight battleground states - about half the number it focused on in 2008.
At the same time, the 2.1 million-member union hopes to get 100,000 of its members to volunteer in its political program, twice as many as in the last presidential race.
Overall, the union is expected to spend at least $85 million to help Obama win, similar to what it spent in 2008.
"It's a matter of figuring out where we can have the greatest impact," said Brandon Davis, the union's national political director. "You'll see an expansion of what we're able to do on the ground by being more efficient with our resources."
The eight states are considered crucial for an Obama victory: Colorado, Florida, New Hampshire, Nevada, Ohio, Pennsylvania, Wisconsin and Virginia.
Davis said the union expects to make 13 million phone calls, knock on 3 million doors and have 1 million one-on-one conversations with voters in those states.
Despite a major setback for organized labor in the Wisconsin recall election on June 5, union households still make up about 25 percent of the national electorate and could be a decisive factor in states with large numbers of union members.
The SEIU played a vital role in helping Obama win in 2008, endorsing him over rival Hillary Rodham Clinton in the Democratic primary. The union's former president, Andy Stern, was one of the most frequent visitors to the White House during Obama's first two years in office.
This year, the union plans to increase outreach to Latino voters in Florida, Nevada and Colorado, black voters in Pennsylvania and Wisconsin, and young voters in all eight states. Davis said the union hopes to register about 600,000 voters around the country, particularly among groups of so-called "low propensity" voters who don't usually participate widely in elections.
"We think that's what creates the margin for the president," Davis said.
The union will also expand canvassing to include the general public in addition to union households, a product of the Supreme Court's landmark campaign finance decision in the case of Citizens United.