If by playing with the integrity of the elections you mean investigating recognised anomalies, and apparent evidence of irregularities and/or fraud, and going through the legal process, then ok.
The Dems have no ability to make Trump concede, nor can they invoke any part of the Constitution to make him. In fact, Biden is announcing his cabinet before the Electoral College has officially voted for him (which honestly I think is a reasonable thing to do).
Trump is not the dictator you think he is.
If the legal process runs its course and claims of fraud or cheating are not proven in court, then we have a legitimately and fairly elected President, and the political battles begin all over again.
Let’s maybe not talk about acting the fool when the Dem candidate can barely finish an English sentence without losing his train of thought or inventing a new word.