Wal-Mart, the world’s largest private employer, announced in a letter to President Obama today that it will support a requirement that all businesses provide health insurance coverage as part of sweeping health reform legislation. The endorsement of the so-called employer mandate represents a dramatic reversal for the retailing giant and a boost for the White House as it tries to inject momentum into its top domestic priority. “We are for shared responsibility,” Wal-Mart President and CEO Mike Duke wrote. “Not every business can make the same contributions, but everyone must make some contribution.” The letter, which was co-signed by the...