Aides and leading donors to Mitt Romney are preparing a major expansion of the campaign’s fund-raising efforts to prepare for a general election contest against President Obama, with the goal of raising up to $600 million, according to several people involved in the discussions. Republican-leaning outside groups and Democratic-leaning unions are planning to spend hundreds of millions more. And Mr. Obama, who raised $750 million in 2008, is likely to meet or exceed that this year, according to people involved in his fund-raising operation. Those goals make it virtually certain that neither party’s nominee will accept public funds for the general election or the spending limits that come with them — the likely death knell for a cornerstone of the post-Watergate campaign finance reforms intended to limit the influence of money in federal elections. Mr. Obama opted out of the public financing program in 2008, breaking a campaign pledge, and went on to outspend the Republican nominee, John McCain, by four to one. “This is going to be the most moneyed election in the history of the United States,” said Bob Edgar, the president of Common Cause, a group that favors greater restrictions on campaign spending. Mr. Edgar, a former congressman who was among the Democratic “Watergate babies” elected in the wake of the scandal, added, “There is a sense of coming full circle, of forgetting our history — the reason we installed a system for financing campaigns that didn’t rely on corporate or wealthy money.” Mr. Obama has already held over a hundred major fund-raisers for his campaign, jointly raising large amounts with the Democratic National Committee, and Mr. Romney is moving quickly to catch up. His campaign is planning dozens of fund-raisers through the end of June, high-dollar events that will feature Mr. Romney as well as the campaign’s top allies and other elected officials. The campaign is setting a goal of raising at least $1 million for most events featuring Mr. Romney personally. Those efforts will be aided by a new joint fund-raising agreement with the Republican National Committee that allows Mr. Romney to command far larger checks than he has during the primaries, when his campaign was limited to increments of $2,500 or less. Under the agreement, guests at major Romney events will be able to write checks as large as $75,000 to a “Romney Victory” committee. About half of that sum would go to Mr. Romney’s campaign or the Republican committee, mimicking the arrangement under which Mr. Obama, as an incumbent, has been raising money since last spring for his campaign and the Democratic National Committee. The remainder will be split among Republican state parties in Massachusetts, Idaho, Oklahoma and Vermont — where party leaders are deemed loyal to Mr. Romney — and later re-allocated to the most critical battleground states. “It’s going to ramp up dramatically,” said Woody Johnson, owner of the New York Jets and one of Mr. Romney’s national finance co-chairmen. “The response I’ve been getting, of people willing to max out on the victory side, has been very very good, very enthusiastic.” Restore Our Future, the “super PAC” whose millions of dollars in negative advertising helped bury Mr. Romney’s Republican rivals, will also shift its focus to the general election, officials familiar with its plans said. The group, which raised more than $43 million through the end of February, is hoping to reach the $100 million mark by the end of the cycle. The super PAC will also have help from Mr. Romney’s allies and backers: Jim Talent, the former United States senator and a key surrogate for Mr. Romney during the primaries, appeared at a Restore Our Future briefing for donors in New York on Wednesday. And people involved with the group’s fund-raising have in recent days approached Sheldon Adelson, the billionaire casino owner whose family contributed over $16 million to a rival super PAC supporting Newt Gingrich, to consider contributing to Restore Our Future. They have also approached Charles and David Koch, the wealthy conservative businessmen who founded Americans for Prosperity, a conservative advocacy group, according to two people with knowledge of the conversations.