I see a couple of advantages. Without polls to tell candidates what they must say in order to garner votes, they would have to campaign on what they believe. No help from the peanut gallery.
It would help voters too. They would actually have to listen to those candidates to find out what they really stand for. No help from the peanut gallery.
Think of it. No more staffs of hundreds plucking and preening appearance nor message. The candidate looks like they look and speaks what they believe. That would eliminate a lot of opportunists who don't believe anything.
It would force voters to figure out for themselves what's important rather than being informed by the polls. They'd hear what the candidates think is important without benefit of polls and could decide for themselves if said candidate is on their wave length rather than blindly hoping.
How ingenious! Everyone thinking without being beholden to any one or any idea other than their own and themselves. Could we cope? I doubt it, but I'd sure like to see it tried!