By Eric Johnson
CHICAGO (Reuters) - President Barack Obama has done what his campaign has asked millions of voters to do for months: go online and donate to his re-election effort.
Obama donated $5,000 to his own campaign, spokeswoman Jennifer Psaki said on Tuesday, providing his Chicago-based team with a small boost after lagging behind in the fundraising race against Republican rival Mitt Romney in recent months.
As a candidate Obama faces no restriction on the amount he can give to his own campaign, but the Democratic incumbent made the donation to underscore what his supporters say is the difference between his own grassroots-style campaign and the big-money outside political action committees he is up against in the bitterly fought race to Election Day.
"On its own, what I gave won't be enough to surmount the unprecedented fundraising we've seen on the other side, both from our opponent's campaign and from the outside groups and special interests supporting him," Obama wrote in an email to supporters on Tuesday.
"But we have always believed that there's nothing we can't do when we all pitch in. That includes me," Obama wrote.
Mitt Romney and his wife, Ann, together donated $150,000 to the former private equity executive's campaign and the Republican National Committee in May.
Despite the Obama campaign's low-dollar messaging, it relies on Priorities USA, a so-called "Super Pac" that has raised millions to benefit the campaign, scores of big-dollar fundraisers and one-off events that have netted millions for the Democratic incumbent.
Restore Our Future, a Super PAC supporting Romney, has raised roughly $81.2 million.
The Obama campaign, whose spending has outpaced the Romney campaign, frequently warns supporters that Obama could be outspent due to the campaign war chests amassed by outside spending groups backing the Republican.
The fundraising gap is narrowing between the two candidates in a record-setting money race to November 6 in what is expected to be the costliest presidential race in U.S. history.
Romney raised about $106 million in June, compared to Obama's roughly $71 million. In May, Romney and his Republican allies edged Obama for the first time, raising more than $76.8 million compared to Obama and wider Democrats' more than $60 million.
Overall, Romney and affiliated Republican groups have raised at least $394.9 million, less than the $552.5 million that Obama and affiliated groups have collected.
(Editing by Cynthia Osterman)