The Dems have won the popular vote in six out of the last seven Presidential elections. They have the numbers fueled by mass immigration and changing demographics. The 2020 race will be close no matter who is the Dem nominee.
Sorry but that argument shows a complete lack of understanding of how presidents are elected. Getting 80% of the vote in California May racknup your national vote total but does not win you the White House.
Dems are looking at a best case scenario not 10 states plus dc this fall regardless of who they nominate.
The Democrats may have had a plurality in 6 of the last 7 Presidential elections, but they got over 50% of the popular vote only in 2 of them (2008 and 2012). In the 49 states outside of California, Trump outpolled Hillary by more than a million votes in 2016.