Democrats

they might try to pull that off for her

Who are "they"? The Democratic party certainly isn't going to be in Sinema's camp if she gets a strong primary challenger, which let's face it, means any primary challenger.

No one in the party is going to stick their neck out to commit massive election fraud to keep her in power, because that's what it would take. If election fraud were a commonplace problem, and the logistical machinery for it was already in existence, even then coming back from such an underwater rating in your own party would be a stretch. But it is not, and it does not. It's simply not a reasonable option, it really doesn't rise even to the level of an unreasonable option.