Let's begin with three facts: First, in the recent election, Republicans posted non-trivial gains in the House, a net gain of nine seats so far. Second, in spite of having many more of their Senators running for reelection in 2020, Republicans only have lost one as yet. Both of these per RealClearPolitics. And third, the modern polarized U.S. is not a ticket-splitting nation, most people vote a straight party ticket.
This raises the question, how did Joe Biden, Democrat, gain more votes than Donald Trump, Republican incumbent. when most Republican incumbents won reelection and several newcomers flipped Democrat House seats? Most of this happened in a few large cities. This outcome seems unlikely unless the fix was in.
Democrats will tell you to ascribe this anomaly to Trump's uniquely obnoxious manner. How does that explain him getting more votes this time than in 2016? Answer: it doesn't. Pollsters found few who voted for Trump in 2016 who planned to vote for Biden in 2020.
Byron York of the Washington Examiner makes some of these same points. This election smells of overripe fish.