https://www.realclearpolitics.com/articles/2019/04/09/evaluating_the_2020_democratic_primary_field_139997.html
Assessing the Democratic presidential primary at this point is a nearly impossible task. With around 15 serious candidates who have declared or formed an exploratory committee, and with another handful seriously looking at joining the race, the slate is very much in flux. Like the Republican primary in 2016, small changes in the polling position of candidates can translate to a large change in their position relative to one another, which in turn incentivizes rising candidates to stay in. So rather than, say, power-ranking the candidates – how does one really decide how to rank John Hickenlooper versus Jay Inslee? – I will look at them through the lens of “buy” versus “sell,” based upon the RCP Poll Average.