Mitt Romney raised significantly more money for his US presidential election campaign last month than Barack Obama, with the Republican contender bringing in a phenomenal $76.8m in May against the president's $60m. That is a sharp increase from April, when Mr Romney and the Republican National Committee raised $40.1m, just shy of the $43.6m pulled in by Mr Obama and the Democrats - a dramatic turnround from 2008, when Mr Obama raised twice as much as his Republican rival John McCain. May was the first full month that Mr Romney has campaigned jointly with the RNC, and the total is likely to alarm Democrats already concerned about the huge financial advantage that Republicans have been amassing through allied outside groups. Indeed, Mr Romney's surprising fundraising power is amplified by the success that the Republican-aligned super-political action committees are having in the first presidential election since the Supreme Court opened the floodgates to outside money. While donations to the candidates" formal campaigns face strict limits, those to the super-Pacs do not. The changes have precipitated a flood of money to Republican-aligned groups, and only a trickle to Democratic ones, despite the fact the president has given the green light to his supporters to donate to groups trying to help him get re-elected. Outside groups have so far raked in $114m since the beginning of 2011, according to calculations by the Sunlight Foundation, which monitors campaign donations. Of that, $44.1m has been spent on supporting Republicans, while a paltry $3.5m has gone to Democrats. Democrats are now waking up to the reality that this year will be different. Obama raised enormous sums in 2008 with an inordinate amount of small donors. There was a belief among Democrats that the money would just magically be there again," said Jim Kessler, a former Democratic aide now at the Third Way think-tank. This is clearly a different time and the Republicans, through their super-Pacs, are raising unheard of amounts of money. The president has embarked on a breathless fundraising blitz as a result, including attending an event at Hollywood star George Clooney's house that is estimated to have raised $15m. Last week the president attended a record six events in a single day, in Minneapolis and Chicago, and this week there were three fundraisers with Bill Clinton in New York, bringing in $3.6m, and five in California on Wednesday and Thursday, raising $5.3m. Mr Obama will next week attend another fundraiser modelled on the Clooney event, this time at Sex and the City star Sarah Jessica Parker's Manhattan home. Mr Romney has been rattling his can this week too, holding back-to-back fundraisers as far afield as Oregon, Utah, Texas, Illinois and New York. But the time and attention Mr Obama is giving to raising cash for his campaign is noteworthy. A Los Angeles breakfast on Thursday morning took to 153 the number of fundraising events he has done since filing for re-election in April last year, according to Mark Knoller, a CBS Radio reporter who compiles presidential statistics. That is almost double the number - 79 - that George W. Bush had done at the same point. Democrats claim the number is misleading, saying that the president's re-election campaign has been much more transparent about fundraisers than Mr Bush's. Mr Obama's re-election campaign said it would "continue to fight hard against the millions of dollars of negative advertising supported by Mitt Romney and his undisclosed special interest allies." The fundraising blitz is a reflection of the increasing awareness within the Obama team that the comparatively weak performance of the super-Pacs that support him could place him at a disadvantage. "This is a response to the enormous amount of money that is coming into the other side through the super-Pacs," said Kathy Kiely of the Sunlight Foundation. The president is stepping up and using what he has got to try to make up the difference. Patti Solis Doyle, who ran Hillary Clinton's 2008 presidential campaign, said Democrats were "concerned but not panicking" at the disparity. "Once all the super-Pac and outside money is all tallied up, Republicans will probably outraise and outspend the Democrats this cycle," she said. It's a problem but it's not like the Obama campaign is crying poor here. They will have enough money to get their message out.