Kriss Riggs isn't one to spend her money on politicians.

"Even the place you can donate a dollar on your taxes, I refuse to do it," says the 60-year-old photographer from Blue River, Ore.

Likewise for Kate Schwartz, a 24-year-old marketing expert from Chicago. Past elections, she says, always seemed far removed from young people.

"A lot of people felt like it wasn't happening in my demographic," Schwartz said.

Not this time.

Riggs and Schwartz are foot soldiers in Barack Obama's 1.5-million-strong army of campaign contributors. Dozens of Associated Press interviews with donors, and an AP financial analysis show how contributions that make only a soft ca-ching by themselves, arriving in increments of $10, $15 and $50, have collectively swelled into a financial roar that has helped propel Obama toward the Democratic president nomination.

Altogether, Obama's campaign has taken in an unprecedented $226 million, most of it contributed online. His donor base is larger than the one the Democratic National Committee had for the 2000 election.

These are hardly political fat cats. Ninety percent of his donors give $100 or less, and 41 percent have given $25 or less, according to the Obama campaign. Overall, he has raised 45 percent of his money in small contributions. Hillary Rodham Clinton's figure is 30 percent, Republican John McCain's is 23 percent.

Riggs and Schwartz are examples of how Obama has become a financial colossus: Neither had given money to a candidate before; both have donated to him more than once; both expect to continue giving. And, just as significantly, they've gone on to help the campaign in other ways, staffing phone banks and canvassing neighborhoods.

In interviews with small donors around the country, the same message comes through: These donors feel they've taken ownership. They believe they're helping to set Obama free from the tug of big-money corporations and special interests.

Says Aaron Alpern, a 46-year-old actor from Chicago: Donors like him "don't have the pull of a gigantic corporation, but we have sort of the reverse _ we give him freedom."

An AP analysis helps to fill in the portrait of Obama's small donors.

They are more broadly dispersed than Clinton's. People whose small contributions to Obama add up to at least $200 can be found in more than 14,000 ZIP codes nationwide, compared with a little less than 12,000 for Clinton, and less than 9,000 for McCain. Conversely, the 10 ZIP codes that contributed the most to Clinton's campaign account for more than 15 percent of her total contributions, while Obama's top 10 ZIP codes account for less than 5 percent of his take. McCain's top 10 ZIP codes account for just over 11 percent of his total.

Obama, a magnet for younger voters, is cashing in on that phenomenon. Among small donors, students have given $303,000 to him, compared with less than $100,000 to Clinton and less than $20,000 to McCain.

Campaigns are not required to disclose detailed information on donors who contribute less than $200, so little is known about the smallest givers. But campaigns do report information on small donors once their combined contributions top the $200 mark.

One such donor is Timothy Sweeney. The 24-year-old medical student at Duke University first noticed Obama when Sweeney was an undergraduate in Chicago, and liked his "high-minded approach to things." Sweeney has donated online in small increments adding up to about $300 so far, and says he may give $100 to $150 more if Obama makes it to the general election.

Obama, says Sweeney, strikes him as "just an honest, decent man, and I felt like somebody like that should be in the race."

Obama also appears to draw a disproportionate amount of support from black donors. In ZIP codes where 90 percent or more of residents are black, the AP analysis found, Obama attracted nearly $150,000 from individuals who gave small donations totaling at least $200, compared with less than $20,000 for Clinton and just $2,140 for McCain.

Obama gets 20 percent of his campaign dollars from the biggest donors, those contributing the maximum $2,300 for the primary campaign, compared to 34 percent for Clinton and 39 percent for McCain, according to the private Campaign Finance Institute.

While little is known about the characteristics of Obama's smallest donors, the impact of their giving is unquestioned.

Their combined purchasing power has turbocharged Obama's campaign, allowing him to do virtually everything he wanted in state after state in the prolonged Democratic duel with Clinton. They also have given Obama the luxury of spending more time talking to the public and less attending fundraisers, and have created a host of supporters working to elect him.

"Anybody that contributes, we immediately call them and ask them if they would like to be part of our organization," says Obama campaign manager David Plouffe. "Every state we go into, we have a foundation of support."

Not only can Obama keep returning to his donors for repeat contributions _ only 2 percent have given the maximum $2,300 _ he still has the potential to increase his pool of contributors from the names on his 3-million-plus e-mail list of contacts. Plouffe stresses that "we don't view our online community as an ATM machine," rather as a network of supporters ready to help in all sorts of ways.

Michael Malbin, executive director of the Campaign Finance Institute, said even the smallest contribution helps voters feel they have a stake in the campaign. Obama, he said, has taken to heart a lesson taught by Saul Alinsky, the father of community organizing, who often spoke about the importance of getting people to contribute even as little as 50 cents to get them invested in a cause. (Obama began his work as a community organizer in Chicago in 1985, more than a decade after Alinsky died, but studied Alinsky's methods.)

"Once a person does anything, that person is likely to do some other thing," Malbin said. In that respect, Malbin said, Obama's small donors are dramatically different from those of Howard Dean, the 2004 Democratic candidate who first tapped into small giving over the Internet but was unable to translate that support into votes.

"It's not just about getting the small gift," said Malbin. "It's about bringing a new person into the campaign, both financially and in terms of the volunteer program, and turning out the vote."

At least 20 percent of Obama's donors never have given to any candidate before, according to Plouffe.

Bonnie Reagan, a 56-year-old consultant from Nashville, is an example. Obama is the first candidate she's ever given to _ more than a dozen contributions so far totaling somewhere under $1,000. And after she gave, she took the campaign up on its invitation to help, and ended up working a phone bank during the early primaries.

Gerald Cook, a 67-year-old retired aerospace engineer in Denver, has $25 for Obama automatically deducted from his checking account each month and then tosses in "a little on top of that." He helped out on the Obama campaign in the lead-up to the Colorado caucuses.

Larry Levine, chair of a community services organization in tiny Hinton, W.Va., gives $50 or $100 every two or three weeks. Hardly anyone would see an Obama sign on his gravel road, he says, but he does keep an Obama sticker in the window of his car.

Riggs, the photographer from Oregon, began making calls for Obama after she began contributing, and even flew to Waco to canvass neighborhoods before the Texas primary.

"I've never done anything" before, said Riggs. "This man has stirred me."

And she's ready to help again.

While the small donors' impact in the immediate race is unquestioned, their future involvement in politics remains an intriguing question mark.

Are these new donors connected only to Obama, or a permanent part of the Democratic political apparatus? Individual donors suggest the answer could go either way.

Dan Cole, a 78-year-old retired teacher from Chicago, said he's willing to look elsewhere should Obama's campaign falter.

"What's of primary importance is that we get a Democrat in the White House," Cole says. "We're not going to fold up our tent and fall back to our hole if it's Hillary or nothing."

But Rosanna Williams, 82, a Philadelphia retiree who has given $500 to Obama in small increments, is adamant.

"If Obama doesn't win, then they can forget about me," she declared.

It could spell trouble for Democrats down the line if Obama's younger supporters don't transfer over.

Anthony Corrado, a campaign finance expert at Colby College in Maine, said there's good reason to think many of Obama's donors won't branch out should his candidacy falter.

"That $25 is their first foray into politics," Corrado said. If Obama doesn't win, he said, "Among these small donors, many will be done. Obama is their candidate."

___

Associated Press writers Ann Sanner, Christine Simmons, David Pace and database editor Troy Thibodeaux contributed to this report.