If you look at the Senate seats that Democrats are trying to flip and the ones they are in danger of losing, it is interesting that they center around the five states Democrats magically "flipped" from Trump to Biden in the wee hours after the 2020 election.
While there is no Michigan Senator running this election cycle, Wisconsin, PA, Arizona, and Georgia are the close races that Dems and the media have focused on most. What a coincidence. These just happen to be the same states where all the questionable voter shenanigans happened in November of 2020. You can throw in Nevada as an additional state dominated by a large population center (Los Vegas in this case) which has a highly effective Democrat political machine (the Reid machine).
These political machines are losing their influence because 1. we are now watching closely for voter fraud and it's more risky to be associated with it, 2. these cities have been under attack by the left (riots, looting, "protest") and rising crime for the past few years, 3. things are so bad under Democrats right now that there are fewer people willing to man these political armies.
IF these political machines continue to decline.. along with ones in Colorado, Washington, Oregon, Minnesota and even Illinois.. many "blue states" will be competitive for the GOP and it will be lights out for the Democrats.