Campaign signs

It's autumn in a US election season, and campaign signs are rising on lawns as leaves are falling.  I've always found this somewhat puzzling, as I don't believe that visibility or quantity of signs for a candidate has ever motivated my vote in that candidate's direction.  Perhaps more often, signs have magnetically repelled my vote, as when they suggest popularity of a candidate that I'm opposing and remind me of my ballot's importance, or if supporters block traffic in their enthusiasm.  I could be more likely to vote for a candidate if I were convinced of their ability to win, but polls (if available) seem like a better basis on which to make that assessment.