* Romney, Republican fundraisers have more to spend
* Obama replenishes funds in record-breaking September
Mitt Romney held a financial advantage over President Barack Obama heading into October thanks to strong fundraising by the Republican Party that will allow its candidate to spend more on the last stretch toward the Nov. 6 election.
Campaign finance disclosures show the Romney campaign, the Republican National Committee and the fund they use jointly had $183.1 million in cash on hand at the end of September, more than Obama and the Democratic Party, who had $149.1 million.
Obama's campaign on its own has dwarfed Romney's in the money stakes in recent months, raising $136.2 million in September, according to a Reuters tally of latest reports. The Romney campaign alone raised much less: $76.1 million, according to filings with the Federal Election Commission.
But when taken together with the RNC, Romney had more to spend on advertising and get-out-the-vote efforts as the campaign entered its last lap with the two men running neck and neck in polls.
September was one of the toughest months for Romney as he lagged in the polls and suffered from the release of a secretly taped video showing him make remarks that 47 percent of the population who receive government benefits are "victims."
Nonetheless, he continued to grow his small-donor base in September and raised nearly a third of his money from checks of less than $200, Saturday's filings showed.
The FEC filings do not account for what the campaign said was a big uptick in online donations after Romney's strong performance in the first presidential debate on Oct. 3.
Romney also has an advantage in support from "Super PACs" and other outside groups such as Republican strategist Karl Rove's nonprofit Crossroads GPS, which funds anti-Obama advertisements.
Republican-aligned groups spent $84.1 million on ads from Sept. 10 through Oct. 18, while pro-Democratic groups laid out less, $23.1 million, despite a strong fundraising month by pro-Obama Super PAC Priorities USA Action, according to Reuters analysis of spending disclosures to the FEC.
The lynchpin of Obama's fundraising effort has been the campaign's ability to collect donations on its own as opposed to the Democratic National Committee or outside-spending groups.
Campaign finance experts say Obama's more direct control of money offers greater flexibility in how to use it. Parties have limits on how much they can coordinate with a candidate's campaign on spending and TV stations promise campaigns - not outside groups or parties - the lowest prices on ads.
However, the ad barrage of the 2012 campaign has boosted prices on precious advertising time in crucial swing states and local TV station managers say campaigns are paying little attention to how much an ad costs as long as it airs in the little time left before Election Day.
Obama's campaign spent a whopping $111.4 million in September, the vast majority of that on the production and airing of ads, according to Reuters analysis of FEC filings. Romney's campaign, by comparison, spent $54.7 million, also mostly on advertising.
SMALL DONOR CHASE
Obama this week released a list of "bundlers" - people raising $50,000 or more for his re-election effort - indicating that so far in this campaign, they helped him with at least $180.1 million. Romney has not disclosed his bundlers.
Romney held his last fundraiser in Florida on Saturday and the Obama campaign had its last one earlier this month.
Obama's prowess with small donors remained on a level with his record-setting 2008 White House bid as he relied on people giving $200 or less for more than a third of his cash this year.
Dollar-to-dollar, Romney's small-donor haul was at least $12.4 million versus $49.5 million for the president, according to a Reuters analysis of data provided to the FEC.
Small donor enthusiasm for Romney lagged through the summer months as he struggled to coalesce the party after the Republican primaries, said Bill Allison, editorial director at the nonpartisan Sunlight Foundation, which advocates for campaign finance transparency.
"Republicans are much more excited about him now," Allison said. Republican small donors include many evangelical conservatives and "they have become the forgotten group in the 2012 campaign," he said.
The RNC had $82.6 million in September, trouncing its Democratic counterpart, which had $4.6 million after taking out a $10.5 million loan.