You asked me "What data should we be basing our opinions on?" and I replied not poll data, that poll data is unnecessary and useless unless you are the candidate using polls to strategize. As a voter your function isn't to plan the campaign, but to vote. One time per election. Instead of basing your vote on polling data you should base it on your own opinion of who is best for the job.
You seem unable to grasp the above, because you then said "Unless your argument is that it's literally impossible to have any indication of how an election might go and therefore the only reasonable approach is for everybody to treat every possibility as equally probable, then you presumably feel that the acquisition of data is possible. It seems that you don't believe polls can fulfil that function, so I'm curious as to what you feel is. "
To which I replied asking why you need to have an indication of how an election might go. Your task is still a vote, not to run the candidate's campaign for them. You still don't need polling data to decide which candidate to vote for.
Unless your criterion for voting for a candidate is to vote for the candidate that the most other people are voting for, in which case you may as well not vote at all. It would be the same result.