Obama campaign manager Jim Messina says the number of contributors to the president’s reelection bid could top 1 million by the end of the month.

“In the 2008 campaign, it took us more than a year to reach that milestone,” Messina wrote in a fundraising email to supporters. “This time around, we could cross it as soon as October — just six months after the launch of the campaign.”

In the second quarter Obama reported donations from more than 550,000 individuals through June 30, nearly half of whom were completely new donors to his organization.

Aides said at the time that the amount of participation — exceeding all of the donors to Obama in 2007 — set a new record for that point in any presidential campaign.  Doubling that number in the third quarter would be equally impressive.

Still, the composition of donors has revealed a stark gap in engagement from 2008.  Of the estimated 3 million Americans who donated to Obama’s first election campaign, only 292,000 had returned to give again through June.

The generosity of his supporters also remains closely watched. Obama and the Democratic National Committee raised a record $86 million combined in April, May and June.

The campaign has set a lower bar of $55 million for July, August and September.