Sen. Carl Levin, a Michigan Democrat, announced his retirement from the Senate on Thursday evening. Until 2014, he'll work hard as chairman of the Senate Armed Services Committee, but after that, it's time to relax. Levin will leave some pretty big shoes to fill, too.

Levin's earned it. As the longest serving senator in Michigan history, the 78-year-old Detroit native has been in the Senate for 35 years now. Not only did he guide our military through September 11 and the two wars that followed, Levin also marched to the front lines of the financial crisis and took a keen interest in bringing down crooked corporations and the reckless executives that run them as chairman of the Senate Permanent Subcommittee on Investigations. In the past couple of decades, Levin's been responsible for exposing the wrongdoings of naughty leaders of every company from Enron to Goldman Sachs.

You probably remember his name from the report he co-authored with Sen. Tom Coburn almost two years ago, "Wall Street and the Financial Crisis: Anatomy of a Financial Collapse" (PDF), and the panel that followed. In that 650-page report, Levin and Coburn pointed fingers not only specific companies like Washington Mutual but also at specific executives like WaMu's former CEO Larry Killinger. And Levin wasn't bashful about his intentions in publishing a phonebook — or at least something the size of a phonebook — full of financial crisis villains. He told The New York Times, "The report pulls back the curtain on shoddy, risky, deceptive practices on the part of a lot of major financial institutions."

So who's going to be pulling back those curtains now, casting light into the dark corners of corporate America? Well we have to see who takes Levin's seat first. Democrats are confident they'll be able to find a candidate, and it helps a little that Levin was popular in his district. Republicans have been working on a list of names since last year when speculation that Levin was almost done started to circulate. As for who's going to do the dirty work in the Investigations Subcommittee, Tom Coburn, a Republican, was a good partner but as an ex officio member, generally wouldn't vote. But out of the remaining names, there is a heck of a frontrunner. 

We'll give you three clues. He shares a name with Ayn Rand. His dad can't stop running for president. And yesterday, he considered wearing a catheter to work. (Spoiler: It's Rand Paul.)