By Laura Smith-Spark
BBC News, Washington
Six months into the race, the Democratic contenders for the White House in 2008 are out-fundraising the Republicans by a wide margin.
Democrat Barack Obama has raised some $17m online in six months
The official second-quarter fundraising results show that the Democrats garnered some $81.2m (£40.6m) between them, compared to $46.6m (£23.3m) for the Republicans.
And a big factor in the Democrats' success is the number of people donating money to their campaigns over the internet.
Of the $58m (£29m) raised by Barack Obama, Senator for Illinois, in the first six months of this year, $17.2m has been given by online donors, $10.3m during the latest quarter.
Fellow Democrat John Edwards, former senator for North Carolina, raised $3.5m online in the second quarter of fundraising, just over a third of the $9m he raised in total. In the first quarter he raised about $3.3m online.
Hillary Clinton, Democratic senator for New York, raised $4.2m over the internet in the first three months of this year - some $600,000 of it in the last 36 hours before the deadline.
While the Republicans have also turned to the internet to solicit donations, their figures are less remarkable.
Mitt Romney, former governor of Massachusetts, is credited with raising $10m online over six months by the New York Times, while Arizona Senator John McCain garnered some $3m.
One exception however is Ron Paul. The anti-war congressman from Texas is considered an outside shot but has built up a devoted internet following, helping to give him about $2m cash on hand - roughly the same as Mr McCain.
So what has given the Democrats the edge when it comes to pulling in the dollars online?
Senator John McCain is not among the top fundraisers on the internet
According to Stephen Hess, of the Brookings Institution, the reason for the Democrats' internet dominance is largely that their supporters are more fired-up.
Fundraising for 2008 is being driven "by the incredible interest on the Democratic side basically in removing George W Bush and winning the election", he says.
The fact that the technology to donate online now exists and makes it easy to make small contributions "right into the political bloodstream" only adds to the momentum, Mr Hess says.
"If it was another 'ho hum' election we would not have had the interest in online campaigning that we have had this time."
Michael Malbin, of the Campaign Finance Institute, argues that the Democrats have been ahead of the Republicans generally in building online communities.
This internet presence has allowed them to sidestep the Republicans' traditional advantage in direct mail marketing - and given the Democrats the chance to gain more than cash.
"Online fundraising is part of a strategy that's not only about money, it's about trying to build networks, building support among people to whom you can go back - people who can be reached at low cost and reached repeatedly," Mr Malbin says.
Patrick Ruffini, a Republican strategist, acknowledges on his blog that the environment "stinks" for the Republicans right now.
In 2008, small change donated online could add up to big change
He writes that he expects online fundraising to "explode" once the race comes down to the general election fight between each party's chosen candidate.
"The question is whether we'll rise enough to keep up," he says, citing a "generational challenge" faced by Republican strategists trying unsuccessfully to adapt direct mail marketing tactics to online campaigning.
"If you view the internet as a shiny new toy, or worse, a new coat of paint on an old jalopy, you're missing the point," he says.
"Increasingly it's becoming the platform from which campaign strategy itself is executed."
The profile of internet fundraising has certainly risen since 2004 when Democratic hopeful Howard Dean demonstrated its power.
A study for the Pew Research Center published last week shows that all 19 officially declared candidates use their websites to solicit donations - and some go further.
Eight of the candidates' sites, four from each party, provide supporters with tools for hosting their own fundraising events, the report by the Project for Excellence in Journalism says.
Republican Rudy Giuliani's site also provides an e-mail letter for supporters to send to friends asking for donations.
As campaigning continues, the value of online donors - many of whom have given well below the $2,300 limit on individual contributions to primary and to general elections - is likely to become ever more apparent.
Howard Dean's internet support did not measure up to a win
Of the 110,000 internet contributors to the Obama campaign in the first six months of the year, nine out of 10 gave $100 or less.
With all their details registered online, his campaign can go back to the same people again and again in the coming months to ask for more, up to the $2,300 ceiling.
And, of course, the beauty of online donations is their simplicity and spontaneity: with a few clicks of the mouse, a person can give what they choose, when they choose.
"You don't have to go to your chequebook, you don't have to put it an envelope, put a stamp on it, you don't have to go to your mailbox - the ease of it is quite marvellous," says Mr Hess.
Nonetheless, he warns against overplaying the power of the internet as the candidates fight for each party's nomination early next year, and then the presidency.
"Dean did all this and his campaign imploded, so this doesn't mean by any means that Barack Obama, who is doing best this way, is going to win the nomination," he says.