In interviews with dozens of low-dollar contributors in the past two weeks, some said they were unhappy with what they viewed as Mr. 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 Mr. 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. Mr. Alasadi contributed repeatedly to Mr. 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,” Mr. Alasadi said.