K. Craig Wildfang’s office on the 23rd floor of a downtown Minneapolis office tower is unremarkable, with little decoration beyond some poster-size travel photos and a smattering of bankers’ boxes and books.

Then there’s the yellow Post-it note on the wall with a number scrawled on it: $5,737,500,000.

That’s the latest value of a settlement Wildfang forged for the nation’s retailers in their battle against Visa, MasterCard and card-issuing banks over swipe fees. The largest private class-action antitrust settlement in U.S. history, the deal aims to resolve a long and bitter conflict over the billions in fees that retailers, and ultimately consumers, pay on card transactions.

Many antitrust experts consider the settlement a remarkable feat. But some retailers despise it as a cop-out that leaves the card giants free to set the fees however they want. The dollar value, first announced last year, has shrunk from $7.25 billion to $5.7 billion after industry powerhouses including Target Corp. have opted out.

Now, after years of legal wrangling, Wildfang is waiting for U.S. District Judge John Gleeson in New York to make a final decision on the deal.

“I devoted seven years of my life to this case,” Wildfang said. “People can disagree with me, but I really did do my best.”

Wildfang, 61, has earned a reputation as one of the country’s top antitrust litigators for plaintiffs. He led the giant case from its inception in 2005, when he filed the original interchange lawsuit for the class action’s first plaintiff, St. Paul businessman Mike Schumann.

The co-owner of Traditions Classic Home Furnishings, Schumann was ultimately one of 7 million to 8 million retailers in the class, just about any merchant who had swiped a credit or debit card since 2004.

It’s been a marathon.

Wildfang’s children, now in college, grew up with “the interchange case.” Along the way, Wildfang developed a chronic back problem that, he admitted, added to the challenge. He blames the bad back on years at desks and on airplanes.

Though he lives in Eden Prairie with his wife and two standard poodles, his work is national. He hasn’t tried a case in Minneapolis in about 15 years.

In his office, he demonstrates a hydraulic workstation that enables him to work part of the day standing up. Four back surgeries have left him with fused vertebrae.

Wildfang argues, as he is wont to do, that $7.25 billion is still the better number for the size of the interchange settlement since it captures the value of relief that opt-outs will get in pursuing their own claims in court. The requested attorneys’ fees have fallen from $720 million to about $570 million, plus $27 million for out-of-pocket expenses.

Robins, Kaplan, Miller & Ciresi, the firm where Wildfang works, hopes to get a quarter to one-third of that, or about $142 million to $190 million for eight years of work. The next largest chunk goes to colead counsels in Philadelphia and San Diego who also were appointed to represent the country’s retailers. But Judge Gleeson could reduce the entire amount.

Not that checks will go out soon. Appeals are a given.

Forceful litigator

Born in Iowa, Wildfang grew up in what he describes as a conservative German family. He was about 4 when the family moved to Bloomington.

After graduating from the University of Minnesota Law School, he tackled a range of cases, even prosecuting a Minneapolis cop for beating a teenage girl with a flashlight.

People who know him describe Wildfang as tenacious, a master litigation strategist who is fond of quoting Winston Churchill, yet who always tried to get home to cook dinner for his children.

By his own count, he’s lost just two antitrust cases in his career.

“I used to joke a lot that Craig’s definition of bad faith is ‘you won’t agree with me,’ ” said longtime friend and colleague Chris Madel. “He’ll just keep digging and digging. He’s relentless on everything.

“When you’re on the other side, you can’t stand him.”

Brooks Poley, a litigator at Winthrop & Weinstine in Minneapolis, recalled working opposite Wildfang on a price-fixing case. One of the lawyers complained to the judge that Wildfang was fighting over every last detail.

“Craig was just being impossible to deal with,” Poley said.

When the judge asked Wildfang about it, Wildfang copped to it. “He said ‘I think my obligation is to represent the class zealously, and that’s what I do,’ ” Poley recalled.

‘A death struggle’

Antitrust issues swirling around Visa and MasterCard caught Wildfang’s attention in the 1990s, while he was in the Clinton administration. Over the years, he became convinced that it would take a broad class action challenging “the whole works” to get true reform.

Enter Mike Schumann.

Every time shoppers use their plastic, retailers like Schumann pay fees to the payments networks and banks, averaging about 2 percent of the purchase price. The fees are the third biggest cost at Schumann’s furniture business, after rent and payroll.

Last year, merchants paid more than $32 billion in interchange fees for Visa and MasterCard credit and debit card payments, according to payments industry newsletter the Nilson Report.

“I watch every bill,” Schumann said in an interview at his store on St. Paul’s Grand Avenue, surrounded by upholstery samples. “I tell everybody that the reason we’re successful is because I look at every PO for toilet paper.”

Fed up, Schumann went online searching for a law firm. Pretty soon, Wildfang showed up in the store.

In 2005, they filed the first interchange case in Connecticut. Interest exploded. Lawsuits were filed everywhere. All of them were consolidated under Gleeson in the Eastern District of New York.

Wildfang said he knew it would be a “death struggle.”

He just didn’t know it would take so long.

Praise and criticism

Antitrust expert John M. Connor, emeritus professor of economics at Purdue University, calls the settlement a remarkable feat.

Wildfang “is very much admired … as an extremely tough litigator who took on an uphill battle against extremely well-financed and well-lawyered defendants,” Connor said. “To have won that case is a great victory.”

David Balto, a former colleague who practices antitrust law in Washington, D.C., said the case demonstrated Wildfang’s skill at team building.

“He’s able to bring together a remarkably diverse set of highly talented people who have overwhelming egos,” Balto said. “I call him the Phil Jackson of antitrust.”

Some big retailers see it differently. They protest that while the settlement allows retailers to surcharge shoppers for using plastic, stores either won’t do it for fear of losing customers or can’t because of state restrictions. They also argue that the deal unfairly prevents them from suing Visa and MasterCard over the same issues in the future and that it ultimately does not check the ability of Visa and MasterCard to set high fees.

Doug Kantor, an attorney representing the National Association of Convenience Stores (NACS), said the deal failed “because our lawyers valued their judgment over their clients’ judgment.”

Four other retail trade groups wrote to the judge in September, accusing Wildfang and his team of cutting them out of vital negotiations and lying to the court about the level of disapproval.

Wildfang rejects the criticism as “just plain not true.” He accuses the NACS of orchestrating a noisy anti-settlement publicity campaign because a deal would undermine the group’s ability to get Congress to regulate interchange fees for credit cards, as it has for debit cards.

Lost in the arguments, Wildfang said, is a crucial point. Back in 2005, the major banks owned Visa and MasterCard outright. A key goal of the original litigation, he said, was to get them to divest their interests in the card networks.

They did. MasterCard went public in 2006 and Visa in 2008. He credits the litigation with accomplishing that.

Schumann, the original plaintiff, expresses mixed feelings. In his view, the negotiations were caught in a lawyers-only process when businesspeople should have been exchanging ideas on fixing the system.

“I fault the legal system. Not Craig,” Schumann said of Wildfang. “He’s got the retailers’ best interest at heart. There’s no question about that.”