Look, I am further left then the average Dem on most issues. However, I'm also pragmatic. For 2020 my only goal is to defeat Trump. Outside of Tulsi Gabbard who has some weird stances on issues, I would be happy to vote for any of the Dems who have announced.
As to who has the best chance to win, my pragmatic side thinks it will be someone not too far left to scare the large number of Americans who are still scared of the big S word. Is it silly that people are scared of socialism but agree with most of the Democratic Socialist ideas bandied about, Yes. However, it is where we still are as a nation. I think the US is ready to move back to the left, but our first priority needs to be to unite to get Trump out of office.