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GOP source: Romney raised more than $100 million in August

Mitt Romney.

(CBS News) For the third straight month, the Romney campaign and supporting GOP committees raked in more than $100 million in fundraising in August, a GOP fundraising source confirms to CBS News.

According to the source, the Romney campaign told donors about the monthly haul in Tampa at the Republican National Convention. According to the same source, the campaign thinks the total will be even higher in September.

In the aftermath of Romney's announcement last month that he had tapped Republican Rep. Paul Ryan, of Wisconsin, to be his vice presidential running mate, the campaign boasted of a huge fundraising boost via Twitter.

"$5 million raised, 70,000+ donations online since @MittRomney announced @PaulRyanVP," wrote Romney press secretary Andrea Saul on August 12, the day after the official announcement.

Despite early predictions that President Obama would be running a billion-dollar campaign, the Romney campaign has outpaced the president in fundraising since May.

Scott Conroy contributed to this report.