It's obviously a terrible situation, but I'm somewhat confident that you couldn't actually throw the election even with complete access. I, for example, always stop by at a polling place a friend volunteers at after the polls are closed and watch them count the ballots. Everyone is free to observe, and you can get as close as you could want, and count the ballots yourself.
There are only a few hundred voters per precinct, so any person can, if they want, verify their (or another) precinct's results end-to-end: count some or all the ballots, then compare with the results posted online.
The volunteers manning the polling places are also incredibly dedicated and professional. I'm pretty sure that at least one of them also verifies the data. It's a diverse crowd (not, for example, party officials or public servants), which makes it practically impossible to get their buy-in to any corruption.