The Obama campaign, which has prided itself on robust engagement of its grassroots supporters, appears to have stumbled in an effort meant to enlist at least 20,000 small donors by the end of September.

A campaign website set up to track the grassroots fundraising competition reported just 11,518 donations through 12:47 p.m. on Sept. 30 — a surprising result given the intensive focus on the program by Obama’s campaign team.

The president himself had  offered a phone call to the two individuals who gathered the most contributions as a top prize.

Obama campaign aides have publicly advertised a $55 million fundraising goal for the third quarter, which ended Friday — a number they’ll likely reach and exceed.

But the outcome of the grassroots challenge could be a sign the total won’t be as impressive, or goal-shattering, as it was the quarter before.

Obama blew past a $60 million goal for the first major fundraising period of the 2012 campaign, from April through June, reporting a whopping $86 million raised for his campaign and the Democratic National Committee combined.   Aides sought at least 450,000 contributors, but ended the three-month sweep with more than 552,000 on board.

Since then, there are signs the campaign has struggled to energize some groups of high-dollar donors, particularly those on Wall Street who had supported his 2008 campaign.  Aides have also cited the cancellation of several fundraisers during the debt ceiling debate and the typical summer-month fundraising doldrums in an effort to lower expectations.

President and Michelle Obama and Vice President Joe Biden have attended more than a dozen fundraisers combined in the past two weeks, hauling in millions of dollars in a hurry after a sluggish start to the period in July. The campaign has hinted that nearly 1 million people have donated to Obama’s re-election bid — close to double the number reported just three months ago.