I really hope we have less than 4 candidates by the Iowa caucus
If first place has less than 40% of the popular vote, that’s going to look awful.
Outside of Hillary Clinton in 2016 (in what was a two and a tenth person race) no opposed candidate has cracked 40% in Iowa since Gore (63%) and Bush (41%) in 2000. (Both Bradley and McCain chose to contest NH; Steve Forbes was second in Iowa, McCain had less than Alan Keyes and Gary Bauer.) Walter Mondale in 1984 is the only candidate to get more than 40% with three or more "significant" candidates in the race
ever and even in that case Jesse Jackson basically did not exist in the state and Gary Hart had just started to take off.
There's really no reason to drop out until after Super Tuesday and most candidates have had other reasons to do so. Beto obviously was tired of the actual process as indicated months ago, with him facing being knocked out of the debates which he hated there was obviously no point.
What the Democrats actually had to fear, and still do to some extent, is their own delegate threshold. Unlike the Republicans, the Democrats only allocate delegates to candidates who get over 15%. If only one candidate gets above that number they get all the delegates. As of right now that's only three candidates nationally, Biden, Warren and Sanders. And add Buttigieg in Iowa. Biden literally cannot win the nomination if we assume this holds through Super Tuesday and Sanders/Warren will back the other.
Buttigieg was a bit much with his declaration of a one-on-one fight with Warren, but in a way, he's technically correct. If Biden supporters, and other candidate supporters, do not want Sanders/Warren, Buttigieg is the only candidate on the table currently. He is strong in both Iowa and NH, and rising nationally. Harris has imploded and is actually worse in Iowa and NH than nationally. Klobuchar is trending the opposite of Harris but she's still borderline irrelevant in the one state she's trying to win, Iowa. Yang, Tulsi and Steyer hold a good chunk of vote both early and nationally. Booker is an enigma candidate. And Buttigieg's rise hasn't only taken from Biden like the early states, nationally it's
taken from Warren, and both him and Biden have gone up nationally as Warren has fallen back towards Sanders.
In any case, Iowa is still three months away.
