St. Louis investor Sam Fox and his son, Jeffrey, serve as co-chairmen of Mitt Romney’s finance operation in Missouri, raising hundreds of thousands of dollars from other Republicans in a crucial battleground state.

But the Foxes also have another way to help the Republican presidential candidate — giving $90,000 each to an independent group, Restore Our Future, that is focused on supporting Romney’s drive for the White House. A third family member, Greg Fox, chipped in $20,000.

“It’s a very sluggish economy, which makes it harder for us to raise money, that’s for sure,” said Sam Fox, a former ambassador to Belgium who founded the family’s Harbour Group investment firm in St. Louis. “So everything that can be done is important.”

The 2010 elections saw the rise of “super PACs,” outside political groups that can raise and spend unlimited amounts of money. The 2012 contest brings “super bundlers,” a new breed of fundraisers who can raise millions for candidates and outside groups at the same time.

Wealthy donors who bundle contributions for candidates have long exercised inordinate influence in U.S. politics, often being rewarded with cushy ambassadorships or powerful positions in Washington. But recent changes in the landscape of campaign-finance law have given these donors even greater influence with candidates and their advisers.

As recently as two years ago, corporations were barred from spending any money on elections and donors were more tightly restricted as to how they could help candidates. But a 2010 Supreme Court ruling effectively swept away the corporate spending ban and other limits, making it easier than it has been in decades to bankroll a high-dollar election effort.

A wealthy donor now has the ability to give nearly $67,000 directly to a presidential candidate and his or her party, plus unlimited amounts to super PACs — which must reveal their donors — and nonprofit advocacy groups, which do not. What’s more, donors can enlist their friends and family in the effort and funnel their largesse through opaque corporations, compounding their influence within a candidate’s inner circle.

The super bundler phenomenon appears confined to Romney and President Obama (D), who are far ahead of their competitors in raising money. But there are signs that other Republican candidates will soon catch up.

Backers of Rep. Michele Bachmann (R-Minn.), whose grass-roots candidacy has relied mostly on small donors, announced a new super PAC last week to help her presidential run.

And Texas Gov. Rick Perry (R), who announced his candidacy over the weekend, has in place a vast fundraising apparatus that includes several super PACs formed by supporters. One new pro-Perry group, Make Us Great Again, will hold its first fundraisers in Texas this week and will begin running ads, organizers said.

Perry has raised more than $100 million during his political career and will be able to draw on a long list of wealthy benefactors from his time as Texas governor and chairman of the Republican Governors Association. One strategy document shows that Perry is thinking big, defining a range of bundlers as broad as Obama’s, with a top category of “Patriots” who will be asked to raise $500,000 or more.

The rise of super bundlers raises a series of thorny, and largely untested, legal questions about the extent of cooperation allowed between campaigns and independent groups. The McCain-Feingold campaign finance law bars agents of a campaign from raising unlimited funds — or “soft money” — but it’s unclear whether super bundlers might fit that definition, legal experts said.

“These kinds of wealthy bundlers now have far more power than they’ve had for some time,” said Paul S. Ryan, a lawyer at the Campaign Legal Center, a watchdog group. “It’s a return to the heyday of soft money.”

At least one of every three donors to Restore Our Future also serves as a top bundler for Romney’s presidential campaign, according to a review of disclosure reports, fundraising lists and other records by The Washington Post. The actual number is certainly higher, but Romney has not released an official list of bundlers as he did in 2008.

Overall, more than three-quarters of the donors to the pro-Romney super PAC, which has raised $12 million, have also given to Romney’s presidential campaign, the analysis shows. Hedge fund billionaire John Paulson, who gave $1 million to Restore Our Future, is slated to host a fundraiser for Romney in the Hamptons this month.

Obama, who has released a list of 244 bundlers who have raised $50,000 or more, has at least two major fundraisers who also gave big to Priorities USA Action, a super PAC formed by two former White House aides.

Hollywood mogul Jeffrey Katzenberg has bundled more than $1 million for Obama’s campaign and has given $2 million to Priorities USA, according to rec­ords and interviews. Chicago media magnate Fred Eychaner, a longtime Democratic fundraiser, gave $500,000 to the super PAC and brought in more than $50,000 for Obama’s campaign. Neither responded to requests for comment.

In addition, about a third of Priorities USA’s donors have contributed to Obama’s campaign, records show. Because the campaign has refused donations from registered lobbyists, several have given to the pro-Obama super PAC instead.

Priorities USA spokesman Bill Burton said there should be “no surprise” that there is overlap between those supporting the campaign and the super PAC, but that “we make sure to abide by any and all coordination rules.” The group also has a nonprofit affiliate that does not report its donors.

“The people who are really interested in helping us out have a deep concern about the role that outside money is going to play in the next election on the other side,” Burton said.

The Federal Election Commission has declared that political candidates are free to raise money for super PACs subject to federal contribution limits. Romney has attended at least one Restore Our Future fundraising event; Obama spokesman Ben LaBolt said the president will not do the same for Priorities USA.

Restore Our Future and the Romney campaign declined to comment on the role played by super bundlers. LaBolt said the Obama campaign will abide by all rules forbidding coordination with super PACs.

Among Romney’s most prolific fundraisers is developer H. Gary Morse, one of six members of the candidate’s Florida finance team with connections to Restore Our Future. Morse’s central Florida retirement community, the Villages of Lake Sumter, cut a $250,000 check to the group, and his wife, Rene Morse, sent an additional $250,000.

The Villages, an age-restricted community dubbed “Florida’s Friendliest Retirement Hometown,” is an obligatory stop for Republicans seeking votes — and money — in the state. Morse has helped direct $100,000 in contributions from employees and residents of the Villages to Romney’s campaign, making the community among the biggest sources of cash for the candidate.

A Morse spokesman did not respond to requests for comment. But Al Cardenas, a former state party chairman who has known Morse for 20 years, said the developer does not come off as a major fundraiser.

“I think he owns one suit, which is about 10 years old,” Cardenas said. “He always wears one pair of jeans and a crumpled shirt. That’s Gary.”

Staff writer T.W. Farnum and staff researcher Lucy Shackelford contributed to this report.