The sitting president was claiming election fraud months before the election even happened [0]. He said that he would accept election results "if I win" years before the election happened [1].

It's not on the media to prove the loser of an election's fraud claim. It's on him. He hasn't provided an ounce of proof. His fraud claims were tried in over 60 different court cases, and the courts found that there was no election fraud [2].

[0] https://twitter.com/realdonaldtrump/status/12500675001900892... [1] https://www.youtube.com/watch?v=KQJzt48wXbA [2] https://www.usatoday.com/in-depth/news/politics/elections/20...