Over at the Stump, Noam has lots of praise for Barack Obama's new ad on Social Security.

And Noam is absolutely right. Social Security is "the loose string that unravels McCain's whole sweater," since it "connects the financial market crisis to people's personal bottom line in a way that's downright alarming." 

But its value goes even beyond that. A successful advertisement makes an effective argument for the election. A really successful advertisement does something else, as well: It helps advance a governing agenda. And I think this ad does that.

This spot doesn't simply remind you that McCain wants to privatize Social Security. It also reminds you that, at a time of great financial volatility, we need programs like Social Security because they protect us from financial misfortune. 

In other words, this isn't just an argument against McCain. It's an argument for a robust social welfare state. If Obama gets elected, that's the argument he's going to make as he tries to enact his domestic agenda.

--Jonathan Cohn