WASHINGTON - Barack Obama's virtual campaign is back in Minnesota.

Building on the massive Internet apparatus that helped him win the presidency, Obama is launching a full-tilt grass-roots campaign to drum up support for his controversial $3.5 trillion budget in politically competitive states and districts where he might be able to sway critical congressional votes.

The centerpiece of the campaign, an e-mail list of more than 13 million supporters nationwide, draws heavily on voters and activists in swing states like Minnesota that were in play at different points in the 2008 presidential election.

Among the supporters is Katie McGee, a St. Paul paralegal who volunteered for the Obama for America campaign last fall. Now it's morphed into Organizing for America -- and she spent Saturday going door-to-door in St. Paul talking about the Obama budget's remaking of the American social contract on health care, education and renewable energy.

"It's challenging," said McGee, noting that on the campaign trail Obama could easily galvanize large enthusiastic crowds. "It's a little less sexy with just the issues. It's 'Why do I have to spend my Saturdays doing this? Didn't we just elect this guy?'"

Arrayed against the campaign are most congressional Republicans, along with some Democrats, who are criticizing the budget as the largest expansion of government spending in history. The looming budget battle will be the first major test of the Obama campaign's continuing grass-roots reach and also may be a defining moment of his presidency.

Obama's budget campaign is relying on a network of groups -- including more than 40 labor, environmental and social justice organizations in Minnesota -- that can be counted on to rev up a $5 million to $7 million ground campaign of phone banks, e-mail blasts and door-knocking on behalf of the White House's new budget.

"This is the biggest, baddest coalition campaign I've ever worked on," said Jeremy Funk of the Democrat-aligned Americans United for Change.

One of the local groups is Environment Minnesota, which is poised to enlist nearly 8,000 e-mail activists in a budget fight that normally draws the close attention only of inside-the-Beltway policy wonks and lobbyists.

"The message is Obama is trying to bring about some of the things he campaigned on," said Samantha Chadwick, an organizer with Environment Minnesota, which supports Obama's $646 billion cap-and-trade plan to curb carbon emissions. "He needs help from the same types of grass-roots people who supported his campaign."

An air war as well

Though largely devised as a ground game, the campaign is also getting some air support in Minnesota. Funk's group, Americans United for Change, has started running AM radio ads to pressure freshman Republican Rep. Erik Paulsen, who voted with Democrats on children's health insurance legislation.

Despite the group's pressure, Paulsen echoes familiar GOP criticisms of the budget, chiefly that it would create an unaffordable public spending spree that will raise taxes, crush business and deepen the national debt.

"I can understand why a PR campaign is needed to find support for these proposals, but it would be better for everyone if they instead focused on passing a fiscally responsible budget," said Paulsen spokesman Luke Friedrich.

As both sides gear up for the coming battle over the budget, Minnesota Democrats are deploying a familiar cast of characters from Obama's successful presidential campaign, including Minneapolis Mayor R.T Rybak.

Rybak, who was joined by U.S. Rep. Keith Ellison at a kick-off for the Minnesota campaign, called on supporters to press Congress to back Obama's budget, though it's still days or weeks in the offing.

Whether the push will work remains to be seen.

"No matter how hard anyone tries, you can't duplicate a campaign in the middle of governing," said Rybak, a co-chairman of Obama's campaign in Minnesota. "But you can tell people who were part of an unprecedented grass-roots movement that their job didn't end with the election, it just began."

The budget campaign's national director, Mitch Stewart, is also a familiar face to Obama volunteers in Minnesota. He was part of the Obama campaign's win over Hillary Rodham Clinton in the state's Democratic caucuses last year.

In an e-mail blast to Obama supporters last week, Stewart anticipated a tough legislative battle, underscoring the need to "bring the conversation back into homes and communities across America."

Virtual Obama

Obama kicked off the campaign with a Web video imploring organizers like McGee to take to the streets on Saturday, "block by block and door by door." In an accompanying e-mail, former campaign manager David Plouffe called the coming budget fight "a once-in-a-lifetime opportunity" to lay the groundwork for Obama's sweeping agenda on energy, health care and education.

Republicans also see the budget as a place to draw lines in the sand on two key Obama proposals: creation of a health care reform fund by limiting tax breaks for the wealthy, and a cap-and-trade plan to curb carbon emissions that they view as a business tax that will hurt consumers and cripple the U.S. economy.

Chadwick and other environmental organizers see the budget's projected $646 billion in cap-and-trade revenue as a chance to invest in a new energy economy based on wind, solar and other renewable resources.

However the debate plays out in Congress, the Obama grass-roots effort depends on communicating the nexus between money and policy. "You can't do anything in government without the money," Rybak said. "That's why this matters so much."

Obama's grass-roots push is not without precedent. To Republican strategist Vin Weber, a former Minnesota congressman, it is reminiscent of the early days of Ronald Reagan's White House, which won a major tax cut with the help of conservative groups flooding Congress with letters and phone calls.

But the key, Weber said, is rallying the troops around a well-defined objective that starts with popular support. "The budget is not the place I'd start the campaign," he said. "It's complicated. It's a little harder to sell."

Obama's shock troops believe they have the public on their side. The election was evidence of that. It's just that the campaign is not over.

"The truth of the matter is it's not a one-election effort," McGee said as she prepared this weekend's door-knocking in St. Paul. "It's for the long-haul."

Kevin Diaz • 202-408-2753