Roughly half a million Americans gave more than $200 to Barack Obama's 2008 presidential campaign, shattering political fundraising records. But this time around, say Ben Smith and Rebecca Elliott at BuzzFeed, 88 percent of those same supporters have yet to donate $200 to the re-election effort. (The Obama camp disputes this analysis, arguing that many of its donors are still giving, just less than $200.) What accounts for the massive dropoff in donors? Here, four theories:

1. Democrats are disappointed in Obama
"Where's the change I can believe in?" gripes one former Obama donor who says she won't re-up this year. Clearly, says BuzzFeed, there's an enthusiasm gap "spurred by the distance between the promise of the campaign and the reality of governing." The complaints are varied — health care, the economy, congressional deadlock — but regardless of the reason, "many of Obama's once die-hard supporters share a disappointment born of high expectations." This reflects my theory that Democrats, more so than Republicans, "are willing to walk away from their own party if they don't get what they wanted," says Joe Gandelman at The Moderate Voice.

2. Supporters can't afford to donate
In 2008, Obama raised most of his money before the financial crash. When he won the Iowa caucuses in January 2008, unemployment was at 4.9 percent; now it's 8.2 percent. That rise has led to more than just disillusionment, says Paul Mirengoff at Power Line. It has also made potential donors "less able to help Obama financially than they were four years ago." Sums up one former donor: "I had more money back then than I do today."

3. They don't think he needs it
Many supporters feel "less urgency in giving to a powerful incumbent than to an upstart candidate," says BuzzFeed. Obama has "plenty of money this year, and he doesn't need mine," says one supporter. Others think that because Obama's bank account is so flush, they'd be better off spending their money where it would have more impact, like on the effort to recall Wisconsin Gov. Scott Walker (R).

4. The Obama-Clinton battle fired up donors
Obama "isn't facing a significant primary this cycle," says James Joyner at Outside the Beltway. Last time around, he didn't officially clinch the Democratic nomination until June, so for months in the winter and spring, he was racking up donations from Americans passionate about seeing Obama beat Hillary Clinton in the primary race. Without that tense precursor, donations are slower this time around.