Don't underestimate the impact of a leaders unpopularity being capable of shifting undecideds on the final day of the campaign.
Our Australian Labor government explained away their previous leaders trailing in preferred PM polls to the conservative party leader and having a -21 favorable rating (35% approved, 56% disapproved) then we were wondering why they underperformed relative to pre election polling...
If people don't like you it makes them much more willing to vote elsewhere.