(CBS News) -- Former Massachusetts governor Mitt Romney has been enjoying a big lead when it comes to campaign fundraising in his race for the presidency.
For two months in a row, Romney and the Republicans have taken in more money than President Barack Obama and the Democrats - raising the possibility that this president, until now the most prodigious fundraiser in politics, could be the first incumbent to be out-raised and out-spent by his opponent.
In June, the president raised $71 million, but he was far outpaced by the Romney campaign, which raised $106 million for Romney. That's two months in a row: in May, Romney had the advantage of about $17 million.
The Obama campaign is sounding the alarm. In an email plea for donations, campaign manager Jim Messina wrote, "(The Republican) gap is getting wider, and if it continues at this pace, it could cost us the election."
It's a sentiment that the president has repeatedly echoed in recent weeks: "I need you to hit the doors," he said. "I need you to make some phone calls. I need you to register your friends, get your family members going."
But it's not for lack of trying. Mr. Obama has been fundraising at an unprecedented rate. He's done 107 fundraisers so far this year, compared to 36 for George W. Bush at this time in his re-election campaign in 2004. He has even made fundraising calls to big donors from Air Force One.
In 2008, Mr. Obama outspent John McCain by roughly three-to-one, buoyed by the enthusiasm of small donors as well as by big money from Wall Street and Hollywood. This year, Wall Street is far less generous, and the small donors far less excited.
Romney has had no trouble raising money from wealthy supporters - this past weekend at estates in the Hamptons, where the price of admission was as high as $75,000 a couple.
The president is also warning supporters about the money from outside groups who can raise unlimited amounts of money where the GOP has financial advantage. "The other side is spending more money than we've ever seen before," Mr. Obama said. "I mean, you've got billionaires just writing $10 million checks. They just, they're spending money like nobody's business."
Obama's fundraising thus far has enabled to get a head start advertising in eight of the key swing states in this election. Mr. Obama's campaign has spent more than $40 million in swing state advertising at this point in the campaign, compared to only $13 million for Romney.
On Tuesday, Mr. Obama will be in Cedar Rapids, Iowa on a campaign trip. Romney will be campaigning in Grand Junction, Colo.