Literally none of them
True. I did one election, 2004, as a fill in on the County Board, for a Democrat slot.
My biggest argument: talking my Republican counter-part into allowing a vote for George W. Bush, when the voter (likely 90) had hand-written the name at the top of the page, instead of filling in the box.
We were doing this in a race no one was reporting/following, looking at provisional ballots, in a runaway race, days after the election.