By Alina Selyukh
WASHINGTON (Reuters) - Presidential candidate Mitt Romney plans to start raising money jointly with the Republican National Committee, people involved in the campaign said on Tuesday, as he shifts focus from the party nomination battle to an expensive election campaign against Democratic President Barack Obama.
Romney is the frontrunner in his party's nominating process but has toughed out a long race due to deep reservations among conservatives, who largely have supported his main rival Rick Santorum. Joining fundraising forces with the RNC should help Romney coalesce Republicans behind him.
A joint fund greatly increases how much a donor can give to help a candidate, thanks to larger contributions allowed for party organizations in addition to the campaign.
Campaigns can take only $2,500 during the primary process and another $2,500 for the general election. With a joint effort, a donor can also give up to $70,800 to the RNC and its local, state and district branches, according to the Federal Election Commission's guidelines for this election.
"Our donors are ready to mobilize for November and understand that, for the Republican nominee to be able to compete with the $1 billion Obama machine, they need to get started now," said Romney campaign spokeswoman Andrea Saul.
RNC spokesman Sean Spicer said the party contacted all four Republicans still vying for nomination, offering a joint fundraising agreement. After an offer is made, it is up to the campaigns to fill out the appropriate paperwork and make plans for fundraising events.
Santorum campaign spokesman Hogan Gidley said his team had no events planned in the immediate future but "we'd be happy to" raise money jointly with the RNC. Spokesmen for Newt Gingrich and Ron Paul did not immediately respond.
According to the Wall Street Journal, which first reported the news, the Gingrich campaign had no plans to work alongside the RNC.
"Today is the day a lot of people are looking at it and saying, it's almost mathematically impossible for anybody else to get it," Barry Wynn, a prominent Romney fundraiser in South Carolina, said of the party nomination.
"When it's pretty obvious to most everyone that this is the nominee, at that point you begin to see this type of machinery put in place," he said of joint fundraising.
Wynn said cranking up fundraising for both the party and the campaign shifts focus to the November general election and the Romney campaign is eyeing a return to states that have already cast votes in the primary nominating contest but offer fertile ground for harvesting big checks.
"There are a number of events that the governor (Romney) wants to pencil in, but I think he's really concentrating on these three primaries today and depending on how it works out, they'll start to ink in these events," Wynn said.
On Tuesday, Romney, a former governor of Massachusetts, was poised for victories in Wisconsin, Maryland and Washington, D.C., which Romney donors hope will solidify his chance to emerge as the nominee.
Obama, facing no challengers within his party, has been raising money in coalition with the Democratic National Committee for months. Two joint funds shared by them brought in $128.7 million by the end of February.
On its own, Obama's campaign, which had roughly $750 million for the 2008 election, had raised $120.1 million by the end of February. The DNC meanwhile had raised $73.4 million.
The Romney campaign reported raising just under $75 million and the RNC nearly $103 million by the end of that month.
(Additional reporting by Alexander Cohen and Steve Holland; Editing by Mary Milliken and Frances Kerry)