I'll second Geopolitical Economy Report. Also, Revolutionary Left Radio is fantastic. The host, Bre is intelligent and charismatic, but more than that he's incredible at finding great guests and doing great interviews. If the episode topic even remotely interests me, the episode itself is almost always 9/10. He is also a part of two other podcasts, Guerilla History and Red Menace, which are also both great.
Blowback has had 3 seasons, all are fantastic.
Actually Existing Socialism has some good episodes, though they haven't been around for too long.
This one isn't expressly political, but The Dollop is amazing. Both the hosts are somewhere on the left, though I'm not sure exactly where. It is easily the funniest podcast I've ever listened to.
It doesn't really fall into the category of podcast, but there's an archivist on youtube called the afromarxist. They have archived speeches and interviews of Parenti, Huey Newton, Betty Shabazz, Angela Davis, Kwame Ture, and a lot more