Come the next Tuesday night or Wednesday morning even if things go roughly as many predict or hope, there will likely be a significant difference between actual ballots and exit polls, and greater difference between actual ballots and pre-election polls. This has happened for at least the last couple elections and some have taken it as meaning there had to be tampering and dirty tricks. There might well be some of that, but ballot and poll mismatch is not evidence of it. No poll is perfect. Not every sample is truly representative. Polling is done hopefully big enough, hopefully often enough, and hopefully good enough to narrow the unknowable.
Iowahawk often posts parody of goings on in the world. One of his recent posts is not a parody but an analysis of statistics. It's not as dry that might sound and he takes care of all the math anyway. It's worth a read.