I think a moderate Democrat is going to have a hard time winning the primary in 2020 if Trump wins. Sanders supporters will be angry at Clinton and the Dem leadership for blowing the election. They would lower the tone down on identity politics and move to the left on economics.
What moderate Democrats are there? Evan Bayh, Henry Cuellar, Gwen Graham, Ralph Northam, and maybe Gavin Newsom are the only ones I could see maybe running for President.
By moderate, I mean anyone more moderate than Clinton. Gavin Newsom yes, but I would also include Kaine.