I spoke to Michael J. Malbin, executive director of the Campaign Finance Institute, about the latest fundraising numbers – and I was particularly intrigued by his recent comment that “more than 8 out of 10 donors who gave in the last presidential election have not weighed in yet… There’s a lot of untapped capacity out there.”

A study of donations made during the first six months of 2007 found that more than 80 percent of people who donated to candidates in the 2008 race did not give money in 2004.

Some of Malbin’s data stunned me. For example, what percentage of Bush’s donors who gave more than $1,000 in 2000 do you think gave to the President again in 2004? I would have guessed in the neighborhood of eighty percent, but the CFI study found that only 31 percent gave again in 2004. For donors of $200 or more, it dropped to 30 percent. What’s more, only 24 percent of Gore donors from 2000 and 21 percent of Bradley donors in 2000 gave to any Democratic presidential candidate in 2004.

“It turns out there’s a lot more churning in the system than the political professionals normally expect,” Malbin said. “We picture a candidate going back to the old list, going to the same old, same old again and again, but not that’s really the way it works. People are constantly coming in and then leaving the pool of donors. Today, there are a lot of old donors who haven’t given yet – and who may not give at all.”

He noted that 2004 was a perfect storm for attracting donors: a polarized electorate; big, important issues that riveted voters; differing candidates with starkly different approaches; and new innovations in technology. But he noted that most donations actually came in after Super Tuesday. “Most of the donors came in at that point after the choice was simplified and sharper. By then it was a choice between the presumptive nominees. Sooner or later, this race is going to be one Republican vs. one Democrat, the choice is going to look more stark, and some donors will be more motivated.”

I would have figured that a Gore or Bradley donor would be almost certain to pick a favorite of the 2004 crop, and do the same again with this year’s selection. But a significant number of donors may be extremely candidate-centered, and not inclined to support a successor even if he or she has similar stands.

“I think in primaries, the decision to donate is very personality-based,” Malbin said. “Especially for the small donor, they get personally invested in the candidate, it’s a statement, ‘this guy is the right guy to be the next president.’”

There are two early indicators in this cycle that Malbin finds interesting. The first is the continued grown Obama’s small donor numbers (even accounting for the cap-purchase theory). Since even a well-financed campaign may have trouble running television ads in 23 states in “Super Duper Tuesday”, a huge database of supporters and volunteers that can be mobilized – and who have provided their contact information to the campaign – may be vital for competing.

Malbin said he is also curious to see what John McCain’s spending rate is, since that was what bedeviled the Arizona senator’s efforts earlier this year.