Jon Lieber, Eurasia Group's head of research and managing director for the firm's coverage of United States political and policy developments, shares his perspective on US politics from Washington, DC.

What we're watching in US Politics this week. The big question is, will the Democrats replace Joe Biden after a disastrous debate performance?

Biden was not sharp in Thursday night's debate, seeming every bit of his 81-year-old. Slurring his speech at times, rambling, making confusing comments about what he was going to do to Medicare. And Donald Trump was able to exploit that, having being high energy, his normal blustery self. Biden was unable to push back against any of the outright lies that Trump was telling and was unable to land any punches, even on Biden's best issues, which include Donald Trump's personal character. So now there's a panic setting in among Democrats, and the question is, can they replace Biden and how would they do so?