John McCainJohn McCainEx-Bush aide Nicolle Wallace to host MSNBC show Meghan McCain: Obama 'a dirty capitalist like the rest of us' Top commander: Don't bet on China reining in North Korea MORE praises American workers and denounces Wall Street in his latest TV ad, blaming "greed" among financial firms and stock traders for current U.S. economic conditions.

Since the collapse of investment bank Lehman Brothers and the sale of financial firm Merrill Lynch Monday, McCain has stumped for reforming Wall Street, alleging greed, waste, and corruption in the nation's financial systems.

That argument has become central to McCain's economic platform, and today's ad is his second this week to advocate for Wall Street reforms.