One year before the US presidential elections, White House hopefuls are awash in more money than ever before, thanks to new federal laws loosening restrictions on campaign fundraising and spending.

Money has always been a necessary lubricant for any successful US political campaign, and some observers estimate the 2012 elections - presidential and legislative - could carry a $6bn price tag.

US candidates know well that one of their most important responsibilities is raising campaign cash. But that won't be a problem for some of the 2012 presidential campaigns, thanks in part to the advent of powerful money-making groups called "super PACS".

The super PACs - ramped up "political action committees" - are flooding campaign coffers and rewriting the rules on how candidates raise cash.

The costs of the 2008 presidential election topped $1bn for the first time in history, and the Washington-based Center for Responsive Politics estimates the 2012 campaigns could cost close to $6bn.

In the past, individuals, unions and corporations in the US were bound by law to strict limits on how much money they could donate to a candidate's own campaign committee: $2,500 per donor for the primary election and $2,500 for the general vote.

But after recent changes in campaign finance laws, these newly empowered PACs are allowed to raise unlimited funds which they can donate to a campaign with few restrictions.

Since the 2008 presidential race, "the biggest change is the growth of these super PACs that can accept unlimited contributions and spend unlimited amounts," said Anthony Corrado, a Professor of Government at Colby College in Waterville, Maine.

"I think that they're going to have a major effect on the presidential race," Mr Corrado, a leading expert on the US campaign finance system, told AFP.

Experts believe, in fact, that the cash-raising potential of super PACs is so great that the 2012 presidential race could be the first in which outside groups actually outspend the candidates.

"You're going to have these outside groups that are capable of taking millions of dollars in, and spending that money in the campaign," Mr Corrado said.

"It really has helped create the perfect vehicle for this new flow of money."

The floodgates were opened after a controversial Supreme Court decision last year - Citizens United v Federal Election Commission - cleared the way for corporate spending on elections.

Until then, the rule was that individuals making a campaign contribution were limited to a legal maximum donation of $2,500.

But the Supreme Court ruled that corporations, unions and other groups could spend unlimited amounts of money on advertisements that favoured the election or defeat of candidates.

As a result, instead of giving money directly to a candidate, big donors now can now give it to the super PAC and allow the group to be responsible for donating the cash to the campaign.

And while earlier campaign donations had to be disclosed, the contributions to super PACs - sometimes in the millions of dollars - usually are made anonymously.

In this Wild West of campaign fundraising, new super PACs seem to sprout up almost every day.

One of the super PACs wielding the biggest checkbook is the conservative "Crossroads GPS," run by ex-president George W Bush's one-time political guru Karl Rove.

Mr Rove's group poured millions into last year's mid-term congressional elections, and some observers feel it had a major impact in many of the races. Now it is planning on stepping up its spending on next year's election races.

Among the best-known presidential campaign super PACs is a group backing former Massachusetts Governor Mitch Romney called "Restore Our Prosperity".

Meanwhile, President Barack Obama's re-election effort is being boosted by a group called "Priorities USA Action".

In the 2008 presidential campaign of then-candidate Mr Obama harnessed the collective power of small donors, some sending in contributions as small as $5, which fuelled his winning White House bid.

But under new campaign finance rules, deep-pocketed big donors, particularly corporations, will be more important than ever. That would seem to give a fundraising edge to Republicans, especially millionaire businessman Mitt Romney, against Mr Obama, the Democratic incumbent.

Mr Obama, who has held his own in attracting corporate donations, is also a darling of liberal Hollywood, which has spent freely on his campaign and may help equalise the Republican cash-raising advantage.

At a fundraising dinner in California and Nevada last week his campaign charged a hefty $35,800 per ticket, most of which went to the Democratic National Committee, the party apparatus, but a good chunk of which was set aside for his re-election effort.