A fundraising laggard for much of the campaign, the political action committee (PAC) backing President Barack Obama raised more than a rival group backing Republican Mitt Romney, the second consecutive month the Democratic group had done so.

The pro-Obama group Priorities USA Action said it raised $15.2 million in September, compared with $14.8 million for the pro-Romney group Restore Our Future, according to filings with the Federal Election Commission.

Restore Our Future, a formidable advertising force whose attack ads on Romney's Republican rivals helped him secure the party's presidential nomination, began the crucial month of October with $16.6 million in cash on hand. On Saturday, Priorities' filings are due to reveal its cash on hand and donors for September.

Early this year, many Democratic donors were reluctant to donate to PACs supporting their party's candidates because they disliked the idea of contributing to attack ads and other negative advertising - a staple of spending by groups known as "Super PACs" because they have no limits on how much they can raise and spend.

In recent months, fundraising for Democratic PACs has accelerated to counter the waves of anti-Obama and anti-Democratic ads from Republican groups.

Meanwhile, the Democratic PACs seeking to help candidates win House of Representatives and Senate seats also saw donations rise in September.

Majority PAC, the group helping Democratic candidates for the Senate, announced on Friday its biggest cash haul since its creation in 2010: $10.4 million in September, and another $9.7 million during the first week of October.

Its sister group, House Majority PAC, also had its best month in September and is on track to double that in October, an aide to the group said.

CONTROL OF CONGRESS

Democrats need a net gain of 25 seats to become the majority party in the 435-seat House, an outcome that most pollsters see as unlikely. Republicans need a net gain of four seats to take control of the Senate. Most pollsters also see that as unlikely.

Scores of Republican PACs and tax-exempt groups have been formed to support Republican House and Senate candidates. Tax-exempt groups do not disclose their finances; disclosures of the most influential Super PAC, American Crossroads, are due later on Saturday.

Restore Our Future, the PAC that supports Romney, reported on Friday that its largest donors included Texas home builder Bob Perry and billionaire Harold Simmons. Perry gave $2 million in September and leads all donors with $10 million contributed to Restore Our Future during this election cycle. Simmons gave $500,000 for the month, increasing his total to the group to $1.3 million.

Republicans showed greater fundraising strength at the party level in September.

The Republican National Committee raised $48.4 million and ended September with $82.6 million in cash on hand. Its Democratic counterpart took out a large loan.

The Democratic National Committee, which has focused on races for the Senate and House, raised $20.3 million in September and borrowed $10.5 million. It ended September $20.5 million in debt, according to its filing with the FEC.

A DNC representative declined to comment on the reason for the debt and how it might affect Democratic candidates in the final two weeks before the election. The party had $4.6 million in cash on hand heading into October.

The RNC reported $9.9 million in debt at the end of September, with its $82.6 million in cash on hand.

Unlike the DNC, the Republican Party has been working closely with its presidential candidate, Romney, who heavily relies on its grassroots operation. On the Democratic side, Obama's campaign has a huge grassroots organization itself and does not need such help from its party.

(Additional reporting by Alexander Cohen; Editing by David Lindsey and Will Dunham)

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