In reality or in perception?
For about a third of the country there can, by definition, be no legitimate result other than a Dump victory. They won't believe anything else and Dump and a sizable portion of the GOP will play to them every step of the way.
The real result will be what it is but the right will simply broadcast an alternate reality in which whatever it wants is the case.
The likelihood right now is, if the election is fair, it will be a pretty strong Biden win around 7-8 points, which will translate into around a 120 EV win. But we're facing the possibility of massive interference by right wing radicals sheltered from some factions within the USG, some state officials, and in some places even local law enforcement. This is going to be the most difficult transition of power since Lincoln.