2020 the Dems can’t win, the purpose of the 2020 candidate is to keep the base engaged and motivated, so the loss at the national level will not translate into an all out slaughter down ballot.
No serious contender wants the nomination because they know Trump will win, so if they are the nominee and lose in 2020, it will be a millstone around their neck for a 2024 run.
So anyone serious, and with half a brain, is only using the 2020 cycle to build up a donor list and start a national organization for their run in 2024... once they have done that they will bow out.
This means the 2020 Dem will either be a past their prime back bencher willing to take one for the team, ala Biden.... Or some not ready for prime time young buck who doesn’t realize the nomination will be the end of their political ambitions.
So, its going to be an ugly nasty battle with Biden eventually being the nominee... or some young radical idiot.... Either way, Trump will eat their lunch.
Trump is no sure bet to win. Besides the damage done by the Mueller investigation and the ongoing multiple investigations by the Dems in the House, the ever changing demographics of the country will give the Dem nominee an advantage. The Dems have won the most votes in six out of the last seven elections. The narrow Trump wins in WI, MI, and PA will be hard to replicate given the Dem organizational ability to GOTV coupled with the use of fraud.
And there is no guarantee that Trump will run in 2020. He may just pack it in and go back to being a billionaire who enjoys life and his family. How much is he willing to sacrifice for this country? The GOP has not given him the support he deserves. His business and his children have been hurt by a rabid anti-Trump media and the Dems.