The ever-resourceful Marc Ambinder of the Atlantic reports that Barack Obama's new ad falsely makes it appear as though the senator passed a gutsy welfare reform bill and slashed welfare rolls.

But Ambinder reports that Obama was only one of the co-sponsors of the bill in the Illinois state Senate, that the Illinois action only put the state in line with the federal welfare reform, and that Obama actually opposed the federal legislation.

The ad, being aired in 18 battleground states starting today, features an announcer saying:

"He worked his way through college and Harvard Law. Turned down big money offers, and helped lift neighborhoods stung by job loss. Fought for workers’ rights. He passed a law to move people from welfare to work, slashed the rolls by eighty percent. Passed tax cuts for workers; health care for kids. As president, he’ll end tax breaks for companies that export jobs, reward those that create jobs in America. And never forget the dignity that comes from work."

However, Ambinder writes, "Notice how the careful omission of a pronoun makes it sound like Obama himself "slashed" welfare -- a nice and defensible trick of the trade. Actually, the word "passed" here is a bit out of context. As other news organizations have noted, Obama co-sponsored the bill, which brought Illinois into compliance with the '96 federal law; legislators don't pass anything. And it passed overwhelmingly -- Democrats and Republicans in the Illinois Senate supported it; there was only one no vote And Obama glosses over his opposition to the '96 federal welfare reform law."