A trio of wealthy Arkansas businessmen joined Republican Mitt Romney's fundraising operation, the campaign announced this week.

Warren Stephens, a billionaire investment banker from Little Rock; Murphy Oil Chairman Claiborne Deming; and John Tyson, president of the poultry-processing giant Tysons' Foods, are Romney for President "finance state co-chairs," according to a news release posted Thursday on the campaign's website.

STORY: 25% of Romney bundlers from financial world

"We are all proud to be a part of the Romney team," Stephens said in a statement. "President Obama has had over three years to fix our economy, and it is clear that he is in over his head. Mitt Romney has a decades-long record of job creation and the pro-growth plan to get the country on the right track. We all look forward to working our hardest to help provide the resources needed to defeat President Obama and turn around the country."

Romney has refused to release a complete list of his fundraisers and how much they have collected from others, bucking a practice of presidential nominees going back to the 2000 election. Romney occasionally announced fundraisers in 2011 to demonstrate support for his candidacy in key states, but those announcements have been rare in recent months.

For a story published Thursday, USA TODAY reviewed invitations, news releases, Federal Election Commission records and other accounts to identify roughly 1,200 individuals raising campaign money for Romney. Among the findings: Executives from the world of finance account for roughly a quarter of his fundraisers, more than any other sector.

In May, Stephens donated $500,000 to a pro-Romney super PAC, Restore Our Future. Stephens, perhaps best known for underwriting Wal-Mart's initial public offering in the 1970s, has been an outspoken critic of the Obama administration and the sweeping Dodd-Frank financial regulation enacted during his tenure.