From the SEC's suit against Goldman Sachs to the financial reform debate in the Senate, the world of Wall Street is once again a hot-button issue. MSNBC's Rachel Maddow sought to cut through the complexities by speaking with an expert: Nobel Prize winner in economics Paul Krugman.

Maddow grilled the New York Times columnist on the dealings of Wall Street banks and efforts by Republican leaders to scrap the financial reform bill. Krugman offered a broad condemnation of the rise of derivatives and other financial instruments, which he argued were detrimental to the U.S. economy.

It's kind of a running game we have here ... You say: "Name a financial innovation that has clearly been beneficial, and you're not allowed to use ATMs." Usually that stops the conversation.

Krugman was equally hard on GOP opposition to reforming Wall Street. "It's obvious [Republicans] are huddling with the bankers, huddling with Wall Street to figure out ways to stop this thing and then claiming what they're doing is preventing future bailouts of Wall Street," he clucked.

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