EVANSTON, Ill. — As she headed into the morning sunshine to talk up President Obama's $3.6 trillion budget proposal, Althea Thomas picked up where she left off Nov. 4, backing the president she helped elect.

"It's the change we all voted on," said Thomas, one of about 40 volunteers who fanned out from the Democratic Party headquarters here with clipboards, pledge cards and a sense of mission.

The Obama administration and the Democratic National Committee opened a new chapter yesterday in their ambitious project to convert the energy from last year's campaign into a force for legislative reform on healthcare, climate change, education and taxes.

More than 1,200 groups from Maine to Hawai'i spent the day gathering signatures in support of Obama's economic plan.

Seeking to create a grass-roots force on a scale never seen before, Obama called the volunteers into action in a video message reminiscent of the 2008 contest. In defense of his budget, under attack from many quarters, he asked his supporters to go "block by block and door by door."

In his Saturday radio address, Obama called his budget "an economic blueprint for our future." He said, "I didn't come here to pass on our problems to the next president or the next generation. I came here to solve them."

The idea of deploying a grass-roots army for legislative purposes is untested. Unlike a political campaign, where ballots produce winners and losers on a fixed date, a policy campaign is amorphous.

"If successful, it would have revolutionary implications for American politics," said Ross K. Baker, a Rutgers University political science professor who counts himself among skeptics. "You can generate an enormous amount of support for an individual personality. It's much harder to do that for a piece of legislation."

Chicago neighborhood organizer Raul Botello acknowledged the successes of Obama's organization, but he questions the skills and the staying power of volunteers loosely affiliated with the new Organizing for America, which operates out of the DNC's headquarters.

"It's pretty clear how much harder organizing is to do than straight advocacy," said Botello, a youth organizer for the Albany Park Neighborhood Council. "It takes a long time, being more methodical — and understanding there will be challenges along the way that are going to impede your attempts."

In the Washington area, David McCracken, a retired teacher, said he was surprised at how readily people signed pledge cards outside a supermarket. Within 15 minutes, four people had signed, and he was soon on his way to make more copies.

Not every volunteer had the same success. In Reston, one voter paused to tell public school teacher Pat Hynes that Obama is "way out of his league" and that the canvassing project was "a waste of our time and our attention spans."

An OFA executive said volunteers will continue to gather pledges through the Internet, phone banks and shoe leather, and deliver them to members of Congress as a budget vote draws near.