The Synetech Group Inc. of Charlottesville, Va., which several Democrats have used, has made finance software for years and offers consulting services. No employees of the firm have made any presidential or congressional contributions this election cycle, records show.
Since last year, it has collected more than $1 million from Clinton, Obama and former candidate John Edwards.
Auburn Quad is another leading processing choice for Democrats. The firm was created by the founders of ActBlue to provide the processing software for that website, Doran said. ActBlue is a clearinghouse and collects donations for thousands of Democratic candidates nationwide.
Edwards raised $4.3 million from ActBlue's website and paid $161,000 in fees to Auburn Quad. Obama has raised at least $278,000 through ActBlue directly and paid at least $45,610 to Auburn Quad.
CyberSource Corp. is the second largest recipient of the fees for Clinton, behind American Express. CyberSource of Mountain View, Calif., works with companies like Google and Home Depot and says it works with half the firms listed in the Dow Jones Industrial Average.
So far, it has collected $623,000 for processing credit-card donations for Clinton. None of the company's 17 listed executives had made discernible donations to any presidential campaign, according to the non-partisan Center for Responsive Politics.
Not all the candidates used companies with strong political ties to process their online donations.
Texas Rep. Ron Paul's bid for the Republican nomination has fallen far short at the ballot box but is widely regarded a model for online fundraising. He relied on TransFirst, a Dallas-based company whose employees appear to have made $13,000 in political contributions, almost all of it to Republicans.
The bulk of former candidate Mitt Romney's identifiable processing fees went to NOVA Information Systems, which was renamed Elavon this month. It is a division of U.S. Bancorp, the sixth largest bank in the nation.
Unlike the politically active figures managing most of McCain's online fundraising, Romney's partners seem uninvolved or mildly supportive of Democrats.
It appears NOVA officials did not make any significant political contributions this election cycle while officials with the parent company have divided $7,030 in political contributions among three presidential candidates, all of them Democrats.
Former candidate Fred Thompson relied on NOVA, a Tennessee-based company, and McCain has used it, too.
Processing fees already may be viewed as an unavoidable expense as basic to campaigning as phone bills and plane tickets.
"Your average online donor is an impulse buyer," said David All, a Washington, D.C.-based consultant who last year founded Slatecard.com, which he hopes to be a Republican answer to ActBlue. So far, the site's donors have raised more than $5,000 for GOP presidential candidates.
In charging a 4.5% flat fee, All said he loses money on small donors, which is hopefully offset by the bigger ones. In any event, he sees the site as filling a critical void for the GOP.
"With online donors, the sooner you can seal the deal, the better," he said. "You're risking not sealing the deal if you can't donate online."
The Arizona Republic and USA TODAY are both owned by Gannett.