I suspect that for some time the only part anyone could be undecided about is whether or not to vote at all. It’s easy to see how someone could reject both major party candidates, but nearly impossible to see how anyone could still see them both as potentially worthy of a vote. This is less of a choice between Tweedledee and Tweedledum and more of a choice between cholera and yellow fever.
I suspect that for some time the only part anyone could be undecided about is whether or not to vote at all. It’s easy to see how someone could reject both major party candidates, but nearly impossible to see how anyone could still see them both as potentially worthy of a vote. This is less of a choice between Tweedledee and Tweedledum and more of a choice between cholera and yellow fever.