COVID precautions are highly stratified by political affiliation: Republicans have received the message that many/all precautions are unnecessary. Many others have followed more cautious recommendations from medical experts. In addition, Republicans received the message the mail voting was inherently more subject to fraud, while Democrats, cautious of COVID and not believing the "fraud" message, frequently votes by mail.

This had the exactly predicted result that Democrats voted by mail significantly more than Republicans, who were much more inclined to vote by person.

Many states report in-person voting very quickly, while mail in votes take more time to process. This, again, had the easily predicted outcome of increasingly the tally of votes for Democratic candidates by a significant margin over Republican mail votes.

A great example of this same phenomenon can be seen in states like Florida that are allowed to count such votes before election day. In those states, the predicted result of increased Democratic early/mail voting was fully born out by the results: Democrats lead the early available result, and as in-person votes on election day were tallied Republican votes significantly outpaced Democratic votes. Of course neither Republicans, or Democrats whose tallies suffered as more in-person results were processed, complained about this or alleged fraud, because again, it was the exactly predicted result

Another consideration is that, while polls weren't perfect, the overall result of the election is supported by the polls. Yes, in any individual state the polls may have been outside the margin of error, but as a whole, and in national polls, the results of the election follow the direction of the polls, and the national popular vote is generally within the margin of error on display in national polls. While still not perfect in this election cycle, pollsters did rethink their methods after 2016, taking steps like weighting education level in their models in accordance with the 2016 outcomes, so it is not surprising that, overall, the polls more closely mirrored the results of the 2020 election.

A final point with respect to the claim that Democrats are good at or routinely cheat in elections. The record of Democratic wins does not support this. If they were excellent at stealing elections, I would not expect them to have lost more than half of the presidential elections in the last 40 years. I would not expect them to occupy less than half of the state Governorships. I would not expect them to be in control of less than half of state legislatures. I would not expect them to lose very tight races in toss-up states. I would not expect election results in specific regions, counties, etc. to closely mirror party affiliation trends in voter registration.

I would expect massive conspiracies that would require thousands of people across the country to collaborate to be just about impossible to hide. I would expect more concrete evidence of voter fraud to appear than claims that typically disappear on close inspection. I would expect the bipartisan group of election officials, poll workers, etc. to include substantial numbers of people from opposing parties to have witnessed systematic irregularities instead of the rare vague suspicion.

In short, no available data has come to light to support any sort of widespread election fraud. Should any of the very small scale allegations being levelled by President Trump's campaign demonstrate concrete evidence, I fully support a rigorous investigation and legal proceeding to bring the incidents to light.