Reputations are contested through years, often decades and centuries. In the case of Trump it is likely that we will first see the establishment of two divergent views on his reputation, and only after a very long time anything that resembles a consensus.
In the UK we've seen development of views on PMs.
* From the 1970s Callaghan, Wilson and Heath have ever worse reviews. Heath in particular has fallen as rumours circulate about his personal life and what he may or may not have done. In the 1970s people were likely to support their political tribe and support or revile according to whether Labour (C&W) or Conservative (Heath). Now I think there is consensus that all three were terrible.
* Thatcher won elections but also became a bogey woman. There were certainly two views. Then there was the "consensus" that she was a marmite politician. Today we are moving to appreciate that she had values and kept to them, that her economic policies (however ghastly at the time) worked - her reputation has gone up.
* Blair likewise won elections and was never quite as disliked by the right as Thatcher by the left. Today we are ever-more concerned about his war in Iraq (with something close to a consensus that it was illegal). His reputation is falling.
* Brown. A solid figure - reputation probably up.
Subsequently we're into politicians who are too recent.
Much of history's judgment of Trump will I think be on outcomes, with three dominating:
- how well the US economy did (pre-pandemic)
- international policy, particularly the only US president for ages not to go to war.
- Middle East, and whether improvements in Israel-Arab relations really are down to his intervention.
Trump is at a nadir right now. It may well be that his reputation will be revised upwards.