I think they will have to really highlight her normal background growing up as much as possible to connect her better with normal Americans who might initially see her as an old, white, Northeast liberal in an ivory tower. Carter and Clinton were Southerners that could play well to a broader demographic and I think that helped for those specific campaigns. Obama was young, dynamic, racially mixed, with a compelling personality and vision. I don't see Warren with these natural advantages starting out but her background is a good story for her campaign. Her populist stances could help with some Clinton defectors who went with Trump but her very strong anti-corporate stances could tweak some specific types of independents too, so they should hear she was a Republican (during general election mostly) in the past to try and show some balance. I think the Democrats should pick someone else personally, but the biggest factor in my humble opinion for 2020 will be the strength of feeling towards/against Trump more than any specific candidate as long as it's not a terrible choice.