Top executives at Bain Capital, Goldman Sachs and other financial houses tied to Mitt Romney have poured millions of dollars into a Super Pac that funded the blitz of attack adverts that played a central role in the former Massachusetts governor's victory in Florida.

According to figures released by the Federal Election Commission at midnight, the Super Pac backing Romney, Restore Our Future, took in about $18m from 200 donors during the second half of last year. Nearly 60 of the donors were firms or rich individuals who gave more than $100,000.

The Super Pac backing Barack Obama and started by former White House staffers, Priorities USA Action, raised just $4.4m over the same period. But the financial filings released by the FEC showed that the president's campaign organisation – which is not a Super Pac and therefore limited to individual donations no larger than $2,500 – raised more than twice as much as Romney's in 2011, bringing in $140m.

The disparity suggests that Romney will be heavily reliant on wealthy donors and big business to finance his run for president, after a supreme court ruling last year opened the way for virtually unlimited funding in support of political candidates by individuals, companies and trades unions.

If Romney does become the Republican nominee, he will also be able to draw on two large independent Super Pacs, Crossroads and Crossroads GPS, which raised more than $50m last year.

Romney raised millions from the financial world, including cash from three donors running hedge funds who gave $1m each.

The other donors to Romney included a total of $750,000 from former colleagues at Bain, and $385,000 from executives at Goldman Sachs.

Bob Perry, a Houston developer who was a leading financier of Swift Boat Veterans for Truth – which smeared the 2004 Democratic presidential candidate John Kerry with accusations he made false claims about his service in Vietnam – gave $1m, as did William Koch, brother of Charles and David Koch, who fund the Tea Party movement.

Among the other major donors were members of the Walton family, which founded Walmart – the single largest employer in the US – who gave more than $200,000; Bill Marriot, the chairman of the Marriott hotel chain; and Patrick Durkin, a lobbyist for Barclays bank.

Among the principal donors to the Super Pac supporting Obama were Jeffrey Katzenberg, chief executive of the hugely successful Dreamworks film company, who gave $2m, and the Service Employees International Union, a trade union with more than 2 million members, which donated $1m.

Separately, the union funded attack adverts against Romney during the Florida primary, principally aimed at Hispanics.

Newt Gingrich has been heavily reliant on a single individual, Sheldon Adelson, who poured a total of $10m in to the pro-Gingrich Super Pac, Winning Our Future, to help deliver the former House speaker victory in the South Carolina primary and coming second in Florida. But the figures do not appear in the FEC filings because the money was donated this year.

The Super Pac supporting Rick Perry, the Texas governor who dropped out of the race before the South Carolina primary, raised $5.5m from ranchers and businessmen in his home state, as well as cash from the Choctaw Nation American tribe in Oklahoma which gave $50,000.

Jon Huntsman's principal donor was his wealthy father.

Among the leading donors to Republican causes was the billionaire Harold Simmons, who gave a total of $6.5m to three Super Pacs – most of which went to American Crossroads with smaller donations to the organisations backing Perry and Gingrich.

The comedian Stephen Colbert's Super Pac, Americans for a Better Tomorrow, Tomorrow, outdid Rick Santorum in raising funds, pulling in $825,000 in donations $200 or less. Santorum's Super Pac raised $725,000.