The venerable public affairs series opens its 53rd season, now under the capable stewardship of moderator Robert Costa, who welcomes guest panelists each week for a famously civil discussion of current political topics. It seems unlikely Costa and his guests will run out of conversational fodder, as the United States inches closer to what promises to be the most contentious presidential campaign in history even as the country is also dealing with a deadly pandemic, economic collapse and a renewed crusade for racial equality.