"Although he's been very successful raising money online, and in small dollar contributions, I think Senator Obama would prefer to be within the system, rather than having to race around the country asking for money," says David Donnelly, national campaigns director of Public Campaign Action Fund, a nonprofit dedicated to improving America's campaign finance laws. "But with the way things are now, anyone who opts in does so at their peril. And of course every presidential candidate makes his or her decision on how to fund their campaign based on what they think will bring them to victory."

Obama of course has been extraordinarily successful at raising money from individual donors, mainly through his website, with nearly half of the $270m he has already raised coming from small donations by individuals. McCain in contrast lags well behind - so it isn't surprising that his campaign wants to tie Obama's hands over financing. In fact, Obama's advantage has already seen him launch a television advertising campaign in 18 states, including Alaska and North Dakota, that Democratic candidates would not be able to afford at this stage of the campaign.

John McCain's senior adviser Charlie Black has upbraided Obama for his decision, saying: "It seems to me if you're trying to change politics in America that this is a step backwards, to move away from public finance, which everybody's always participated in, rather than a change for the better." But is the fact that "everybody's always participated in" it any reason to continue doing it - especially if you're trying to effect change? Black has rhetorically invalidated himself.

But beyond any semantic sparring - and more to the point - it's Obama who seems truly committed to reforming the finance system, at this point. As Donelly writes: "McCain once authored a fix to the broken presidential public financing system but now refuses to add his name as cosponsor to the same bipartisan legislation." Obama, by contrast, has co-sponsored the same bill and says he would make passing it a priority if elected. Among other things, that would free up about $200m in taxpayers' money for more useful purposes.

Donelly also points out that while McCain has complained about the undue influence of lobbyists when it comes to electing politicians, McCain himself has five times as many lobbyists raising money for his campaign as Obama does: 70 to 14, according to Public Citizen. It doesn't take a statistical genius to realise that's one lopsided fight."