How likely is a one-term Trump and then a one-term Democratic successor?

[Skill and Chance]

Reasonably possible because Trump is polarizing enough that he could narrowly lose in a very good economy and then the next serious downturn happens during 2021-24 under the next Dem.   

[Skill and Chance]

If Trump is a one-termer, he's gotten himself completely Cartered.

I'd be more certain of 2028 going to Democrats ala Bush Sr than a one-term Democrat right after Trump at this point.

Could be more like Harrison losing in 1892



Also Carter lost because of how bad the shape of the nation was in 1980 not because he was a scandalous president , and hated because of his personality  .

This is interesting.  Trump does seem a lot like Harrison- elected in an EV/PV split while his party controlled Congress, very into tariffs and more into government spending than much of his party, and also pushing back unsuccessfully against a growing national consensus on civil rights issues (though Harrison was pushing in the opposite direction as Trump and almost got an early version of the VRA through congress).

Of course, even though Democrats didn't control the federal government for 16 years after Cleveland's economically disastrous 2nd term ended, public policy generally evolved in a direction Cleveland would have favored, with any real breakthroughs for Harrison's vision many decades off.

[Skill and Chance]

Unlikely, but far from impossible.  Trump doesn't really have any ground he can lose and still win reelection.  A mild recession that turns into a deeper recession/collapse a couple years later is the most likely scenario for this to happen.

[Skill and Chance]

I don't think it's very likely. I also think he'll probably win reelection.

Yeah, i think that dems make big gains in 2018 and that re-energizes conservative voters behind trump and he ends up winning narrowly again in 2020. Plus americans generally don't like kicking presidents out after one term unless they majorly screw up. As long as the economy is fine, i believe trump has a decent shot at being re-elected.

This is my expected outcome.  Not sure what you have in mind by narrowly, but I do think Trump gets the PV next time, but only by 1 or 2% unless he's gone full Bill Clinton with an opposition congress.