From First Read:

Interviewed on MSNBC, Obama strategist David Axelrod revealed that 4 million individuals have now donated to the Obama camp. That’s up from 2.5 million last month, meaning -- if our math is correct -- that 1.5 million new people gave money to Obama. So how big will Obama’s September fundraising haul be? It looks like it might be BIG. Will it top the 100-million mark? (1.5 million new donors at 100 a pop… Well, you get the math.)

Wow. I mean--wow. If Obama really added 1.5 million donors last month, then I'd say $100 million is a pretty conservative fundraising estimate. Remarkable.

Update: It occurs to me that the numbers could be somewhat exaggerated by all the "donors" the Obama campaign signs up at fundraising concerts or when selling T-shirts and key chains. Still, even if that stuff accounts for several hundred thousand people, we're talking about an enormous increase here. (And there's no reason to think the donor-base inflation would be more pronounced now than in the past.) 

Second update: A campaign aide tells Ben Smith that Axelrod misspoke--the 4 million number is too high. Not sure if that means the real number is 3.9 million, or closer to 2.5 million. We'll find out in a couple of days...

--Noam Scheiber