Wal-Mart made “many CEOs choke on their coffee this morning,” said Bernhard Warner and Matthew Yeomans in Slate’s The Big Money. Once “the poster child for corporate villainy,” Wal-Mart is now backing President Obama’s proposal to force employers to provide health insurance for their workers. That’s a big assist to Obama, coming from America’s “largest private employer.”

“The idea of the notoriously cheap chain favoring liberal reforms might seem like a shock,” said Peter Suderman in Reason, but Wal-Mart CEO Lee Scott backed universal health care two years ago. There are also at least two good reasons for Wal-Mart to back an employer mandate: “good PR,” and good business. Wal-Mart can afford it; “smaller competitors” can’t.

That’s certainly how the Chamber of Commerce sees it, said Matthew Yglesias in Think Progress, and the Chamber isn’t happy. But “change is in the air,” and it’s splintering the “highly ideological” business coalition that has held sway over U.S. politics for 30 years. So Wal-Mart’s endorsement is a big boost to Obama’s health plans, but it’s also a big, visible crack in the Chamber’s hold on big business.