I'd be curious to see a proper academic study by a smart non-biased history professor taking a look at historical US Presidential elections for which data is available and estimating:

• the degree to which the election was fair. This should include not only outright fraud on the day of the election but corruption and undermining leading up to it (such as culling of legitimate voters from the lists of registered voters, before the day of the election).

• a binary statement estimating whether the correct party won.

• some estimate for each election of whether the electoral college system helped or hurt the fairness of the election. On this point, my own point here is that arguments about the Electoral College System sometimes leave out what I think is a strength of it. As far as I can tell, it helps triage voting corruption situations so that they do not bleed over from state to state. If we had a dead-simple system where there was simply a single national vote and the person with the most legitimate votes won, there are certainly arguments for this, but one argument against it is that corruption in one state could impact the entire vote much more strongly. So, for example, right now, if one state improperly removes 200,000 legitimate voters from its lists of registered voters, and this ends up dramatically favoring one candidate over another to the point of swaying the election in that state, then under the system at present as I understand it, for most or all states this would award the electoral votes to that favored candidate, but just for that state. Under a simpler proposed national system with no electoral college, even if most states had a really spectacular fairness in their systems, if some states manufactured a few million votes here or there, or prevented a few million legitimate voters from voting, then the national outcome could be impacted beyond what we have seen under the electoral college system. At least, that's my concern.

Again, we have a President - and his supporters - who are openly and brazenly hostile to attempts to protect the American voting system.

[nytimes.com]
Russia Targeted Election Systems in All 50 States, Report Finds
By David E. Sanger and Catie Edmondson
July 25, 2019