The American political system is being challenged in unprecedented ways, but that doesn't mean it hasn't been challenged before. The Mueller investigation into Donald Trump is just the latest of over a dozen special investigations ordered since the US Civil War. But there are two in the last 50 years which are seen as historical references for what’s happening right now - Watergate, and the Lewinsky Scandal. One led to a resignation. The other led to an impeachment. We spoke to Leon Neyfakh, a man who has delved deeply into both those investigations for his wildly successful podcast, Slow Burn, and learned a lot of lessons which should be remembered while talking about the Russia investigation.