DNC - I really hope the DNC learns their lesson from 2016 and hosts the convention in Alabama or Georgia. Both important states - the Democratic Party has been making improvement in both, even picking up a win in Alabama with Doug Jones. Spreading the DNC message into seemingly hostile but opportunistic territory like Georgia could influence some to join the blue wave in 2020.
Don't think Alabama makes any sense, but going to Atlanta, Georgia would be a solid pick (although Atlanta in July might be a bit on the warm side for some of the northern delegates). Alternately, Milwaukee as mentioned, or maybe Minneapolis.