Ok, how popular is President Trump? Fivethirtyeight: 41.6 (note: this reference lists comparisons to past presidents) and Real Clear: 43.9.
Of interest is Trump’s approval among Republicans: it is in the mid 70’s by this poll:
So, while former Governor William Weld will attempt to challenge him for the nomination, I expect the challenge to gain no traction at all.
The race will be on the Democratic side, and do we have a number of candidates. As of right now: Joe Biden and Bernie Sanders lead and of my “favorite 3”, only Kamala Harris has any traction at all (I also like Corey Booker and Amy Klobuchar).
It is early though and who knows where things will lead.