With up to two dozen or more Democrats as Presidential contenders, history tells us that such candidates MUST win their home or regional state primary or caucus in 2020 to survive to later battles.
As a result, we will see winnowing down of candidates during the month of February and early March 2020, after some candidates drop out as a result of a poor performance (by comparison and journalistic judgment) at upcoming debates being held monthly starting in late June and the early primaries and caucuses.
So IF Bernie Sanders or Elizabeth Warren fail to win New Hampshire and or Massachusetts. their candidacies will be effectively over.
So IF Amy Klobuchar, or Pete Buttigieg, or Tim Ryan fail to win Iowa or Minnesota or Michigan or Ohio or Missouri, their candidacies are dead in the water.
So if Julian Castro or Beto O’Rourke fail to win Texas, they will be knocked out of the race for the White House.
So if Kamala Harris or Cory Booker cannot win in South Carolina, with its heavily African American Democratic registration, their Presidential candidacies are doomed.
So if Kamala Harris, or Eric Swalwell, or Tulsi Gabbard, or Jay Inslee, or John Hickenlooper fail to win California or Nevada or Washington, their campaigns will effectively end.
All of the states mentioned above have their primaries or caucuses taking place between February 3 and March 10.
The state of New York will also have its primaries in either February or early March, still undetermined, and Cory Booker or Kirsten Gillibrand would be expected to win that state in order to survive for a longer period.
Notice that the one “national” candidate who does not need to win any specific state or group of states to be viable is former Vice President Joe Biden, who could lose some, win some, but would likely have greater staying power in the race than anyone else.
So by the “Ides Of March” (March 15 or two days later, March 17, when Florida, Arizona, Illinois, and Colorado have had their primaries), we are likely to know who the Democratic nominee is for President.