With 20 folks in the race, and none of them standouts, it will get very ugly, and fast. Of course, when HRC announces, the party will quickly be over for many of them.
The GOP in 2016 had one candidate drop out before Iowa. This time, the Dems already have one, the guy from WV, but I suspect we will have upwards of 8-10 more drop out before the first primary.