Wal-Mart and Big Labor are perfect enemies. The nonunion retailer's entire business model is based around keeping costs low, including labor costs. It has been extraordinarily successful too, but unions now think they have found its weak spot: the company's supply chain.

A major part of Wal-Mart's success has been its extraordinarily efficient logistical system. It maintains one of the world's largest private communications networks as well as massive databases on sales and merchandise.

The company can find needed goods in inventory and ship them out in record time. This year, it began testing same-day delivery for online purchases.

Big Labor has lately been attempting to organize work stoppages at warehouses and other facilities used by the retailer. They've had some modest successes.

In June, eight Mexican guest workers walked off the job at CJ's Seafood in Breaux Bridge, La., a company that supplies Wal-Mart. They later filed a complaint against the supplier with the Labor Department. Wal-Mart has reportedly suspended the supplier.

There have been strikes at various company warehouses in California. A strike at a major supply center in Elwood, Ill., lasted for three weeks. Those strikers eventually got the attention of top officials as well as pay for the time on strike and the reinstatement of four fired workers.

Wal-Mart was willing to deal in part because those strikers weren't Wal-Mart employees. Although it owns the warehouse, the workers were actually employed by a temp agency with whom Wal-Mart contracted -- a standard arrangement within its supply chain.

So the company apparently felt it wasn't giving unions much of a toehold. After all, if the workers did organize, Wal-Mart can just find a new contractor.

Nevertheless, the stories have become a cause celebre on left-wing websites and magazines. They represent some of the first victories, no matter how minor, that organized labor can claim against the retail giant.

"Wal-Mart's increased willingness to meet with [these] workers ... reflect the disproportionate power such workers have to disrupt Wal-Mart's business," wrote labor writer Josh Eidelson in the Nation.

"This [Elwood supply center] is very strategic," Leah Fried, an organizer involved with the Illinois strike, told the magazine Labor Notes. "It's at the heart of Wal-Mart. You clog it up, you can give Wal-Mart a heart attack."

It is certainly a more promising avenue of attack for them than what they have been doing up till now. Big Labor has had a tough time bringing the nation's largest private employer (1.4 million employees) to heel. Repeated efforts to organize workers at stores have fizzled out. A high-profile attempt to organize mass walkouts on Black Friday, i.e., the day after Thanksgiving, became an embarrassment when hardly any workers joined in. Local media reported the unions were instead busing in protesters. In many cases, only one or two protesters worked in the stores. Wal-Mart headquarters claimed only 50 workers walked out nationwide.

Unions also launched aggressive anti-Wal-Mart PR campaigns in 2005. The United Food and Commercial Workers funded a group called Wake Up Wal-Mart, and the Service Employees International Union backed one called Walmart Watch. The latter scored some hits with unflattering leaked internal company documents, but it never came to much.

What momentum the unions had ground to halt once the recession hit. Wal-Mart's low prices proved to be a lifeline for many, and that made it hard for criticism to stick. The unions subsequently pulled the plug on both of their front groups.

They're now betting they can humble the retailer through its supply chain, by robbing it of its competitive advantage. The Nation calls it "a necessary task if there's ever to be a robust future for the US labor movement." If Wal-Mart stops offering those "low, low prices," we'll know why.

Sean Higgins (shiggins@washington examiner.com) is a senior editorial writer for The Washington Examiner. Follow him on Twitter at @seanghiggins.