This may prove to be a very unpopular opinion but I think its the Dem's best option

I was reading an article today showing that Biden and Warren are both building strong coalitions within the Democratic Party. Biden solidly has voters that are moderate, older, as well as large amounts of support among minorities and those in the midwest/rust belt areas. Warren is doing extremely well among younger Democrats, liberals, and those with a college education. Essentially the two major wings of the Democratic Party.

Polls still show, on average, that Biden holds a decent lead and while it is early, does extremely well against Trump. I say that if Biden is the nominee, which from where I'm standing looks like the likely outcome (I know its not guaranteed but if he is the nominee), then the Democrats run a Biden/Warren ticket in 2020. I think would unite the Democrats, Trump would be swept from office, and we achieve probably the biggest goal of our time.

I would say then Biden serves for 1 term (despite what some people say I think he is still in great shape but I don't know about him serving until he is in his mid 80's) and then the Dems run Warren in 2024. Biden does one last great thing for the country by chasing Trump out of the white house, he gets his place in history which he has definitely earned, he spends the rest of his life as the elder statesman for the country, and then Warren leads the country into the future.

Again, I'm sure most people will stick their noses up at the idea of Warren not being the nominee in 2020 or Biden not serving two terms, depending on which side you are on but I think long term that would be the perfect scenario for the Democrats and this country.