Every election people complain about fraud. There is some fraud but imo a lot of it is just a wash out, meaning fraud in NY and CA and IL don’t matter much those states were likely DEM anyway. If fraud mattered a lot, then we would not have seen that massive GOP sweep in 2010. The biggest change in Congressional control since the civil war. If fraud is going to matter, it matters only if the turnout is low. Every 1% is nearly 1.3 million votes so if turnout is 4%-6% higher than normal it is too many to overcome by fraud. You cannot manufacture millions of votes that easily, imo of course.
Apple’s and oranges.
The presidential election is based on the electoral college. An entire state’s electors can be thrown in 1 inner city voting precinct.