FedEx had signed a contract with Boeing to buy two or three dozen new cargo aircraft, which were to be constructed and delivered over the course of several years. The contract contained a provision that allowed FedEx to back out of the deal up to a certain date.
Sen. Patty Murray of Washington, where Boeing is headquartered and where the aircraft would be built, is a ranking member of the Senate committee that drew up the Senate version of the "card check" legislation.
As the legislation was being crafted, the CEO of FedEx made the details of the Boeing contract public, and made it very clear in various media outlets that FedEx would opt out of the Boeing contract and cancel the order for all those new aircraft if the Senate version of that "card check" bill ever saw the light of day. So Murray was put in a position where she could sponsor a Senate bill to benefit organized labor across the country, or she could protect thousands of Boing jobs (union jobs) in her own state. That "card check" bill has now been buried in Murray's Senate committee for five years, and it ain't going anywhere.