They were once among President Barack Obama's most loyal supporters and a potent symbol of his political brand: voters of moderate means who dug deep for the candidate and his message of hope and change, sending him $10 or $25 or $50 every few weeks or months.

But in recent months, the frustration and disillusionment that have dragged down Obama's approval ratings have crept into the ranks of his vaunted small-donor army, underscoring the challenges he faces as he seeks to rekindle grass-roots enthusiasm for his re-election bid.

In interviews with dozens of low-dollar contributors in the past two weeks, some said they were unhappy with what they viewed as Obama's overly conciliatory approach to congressional Republicans.

Others cited what they saw as a lack of passion in the president or said the sour economy had drained both their enthusiasm and their pocketbooks.

For still others, high hopes that Obama would deliver a new kind of politics in his first term have been dashed by the emergence of something that, to them, more resembles politics as usual.

"When I was pro-Obama in 2008, I was thinking of him as a leader who could face the challenges that we were tackling," said Adnan Alasadi, who works in behavioral health in Mesa, Ariz.

Alasadi contributed repeatedly to Obama during his first campaign but says he will not give the president – or anyone else – any more money.

"Now I am seeing him as just an opportunistic politician," Alasadi said.

Such defections are not merely symbolic. About a quarter of Obama's record haul during the 2008 cycle came from donors giving $200 or less, supporters who could be tapped again and again without hitting federal contribution limits. Many of those same people were also volunteers in his campaign, knocking on doors, calling friends and neighbors and helping turn out the voters that fall.

Unhappiness with Obama can be found even among the supporters his team recruited to appear in campaign materials.

When Obama formally announced his re-election bid in April, his campaign released a video featuring supporters from swing states like Colorado and Michigan. One of them was Edward Blair, a 65-year-old lawyer from North Carolina, who sent a half-dozen checks to Obama during the last campaign and knocked on doors in his hometown, Lenoir, but has not given him money this year.

"What I said in that video was I didn't agree with Obama on everything, but I respected him and trusted him," Blair said in a recent interview. But Obama's decision this month to abandon stricter new smog regulations, Blair said, had renewed his worries about the president's ability to lead.

"I certainly respect him, and I trust him," Blair said. "But I am disappointed, and I'm bewildered."

Compared with his Republican rivals, Obama remains in an enviable position. No Republican candidate for president has built a grass-roots fundraising machine as formidable or sophisticated as his.

Through June 30, the close of the most recent campaign reporting period, more than 552,000 people had contributed to Obama's re-election effort, according to campaign officials. Half of them were new donors, and nearly all of them gave contributions of less than $250.

But those figures obscured another statistic: A vast majority of Obama's past donors, who number close to 4 million, have not yet given him any money at all.

The campaign is still in its early stages, and the president is likely to show far stronger numbers than any Republican when the candidates report their third-quarter fundraising early next month.

But his recent political difficulties – a battle over raising the national debt limit, sagging approval ratings – have raised questions about whether he will be able to sustain fundraising momentum.

Aides to Obama said the campaign was well ahead of its 2008 benchmarks. That year, Obama did not reach 1 million total donors until February, about a month after he won the Iowa caucuses.

A campaign spokesman said that the number of people who had given more than once to Obama this year and the number of people who had contributed for the first time were both higher than his total number of donors at the same point in 2007.

This month, the Obama campaign is staging a "Grass-roots Fundraising Challenge," a contest for Obama supporters who have set up fundraising websites for him, with the goal of raising 20,000 contributions by the end of September.

Obama has also provided "grass-roots fundraising tips" on his Twitter feed. "Make a hard ask," one entry read. "Be clear about what you want and when you need it."

Obama's campaign is deploying volunteers to contact all his past supporters one by one, in part to ensure that they have a chance to voice any concerns or criticisms they may have. The campaign also plans to roll out an initiative that will provide donors with real-life examples of how the campaign is spending their dollars to build a field operation in critical states.

But some of Obama's supporters, echoing concerns expressed by many Democrats in polls, said they were less interested in what he would do with their contributions than in seeing him play tougher.

"There has been less passion than I might have hoped for," said Andra Bohnet, a musician and professor in Mobile, Ala., who sent Obama five checks in 2008. "I think that in some ways, they have been too conciliatory."

Asked whether she would give to him again, Bohnet paused.

"Now, I think I'll wait and see," she said.

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