And then there were one
We've seen this show before. The 2020 primaries are looking a lot like the 2016 primaries. The main differences are who is in the cast and the size of the casts. 2016 was for the most part a two-person play with Hillary Clinton and Bernie Sanders as the two lead actors. 2020 is is more like a Agatha Christie murder mystery. The 2020 primary started with more than two dozen characters. These characters in the 2020 version meet their demise with regularity.
2020 and 2016 are the same in the regard that both Democratic primaries pit the centrist Democrats against the progressive Democrats.
Here are the remaining 2020 centrist candidates and their most recent RCP poll averages
Biden is at 16.5%
Bloomberg is at 15.8%
Buttigieg is at 10.8%
Klobuchar is at 6.8%
Steyer is at 1.8% Centrist total is 51.7%
Here are the 2020 progressive candidates and their most recent RCP poll averages
Sanders is at 27.3%
Warren is at 12.8%
Gabbard is at 1.7% Progressive total is 41.8%
The 2020 centrist and progressive totals ad up to only 93.5. The remainder are the undecideds, the no response, the not sure people, etc. To reach 100% exclude from the polling numbers those without an opinion, then the centrist total is 55.3% and the progressive total is 44.7%.
In the 2016 Democratic primary the centrist wing, with Hillary Clinton as their candidate won 16,914,722 of the popular vote. On the progressive side, Bernie Sanders won 13,206,428 of the primary votes. Clinton won 55.2% of the vote to Sanders' 43.1% of the vote. The remaining 1.7% of the primary vote went to Martin O'Malley, who dropped out right after the 2016 Iowa caucuses. He would be in the centrist camp.
That puts the 2016 centrists (Clinton and O'Malley) at 56.9% and the progressives (Sanders) at 43.1%.
The numbers don't lie
In both 2016 and 2020, among Democratic primary voters, there is a distinct preference---of more than ten points---for the moderate candidates over progressive candidates.
In 2020 we don't know who the final two candidates will be, although Sanders looks likely to one of the two. If the race winnows done to Sanders and a centrist candidate, don't be surprised if Sanders receives a very similar percent of the popular primary vote again.