Obama's half a million on fundraising (compared to Clinton's $100k) might explain his larger number of small dollar donors. Although you'd think spending five times as much would net you more than one and a half times as many donors.
with a list of around 250K donors from Bill's days. From that starting point, she ended up with about 50K donors.
... that she has a lot of untapped money hanging out there
On the other hand she appears to have more maxed out donors. Some signs go one way, some the other, and the second quarter numbers could easily benefit either or neither of them.
Obama is going to have a money lead at the end of the second quarter...according to the people that track these kinda things at AU.