That's just preference and the polls have a TON of undecideds. However, elections are not won by getting people to prefer you, but by people actually showing up to the polls to vote for you and I don't think people are going to show up to vote for Trump. On the other hand, I think people will show up to vote against Trump. Throw in the Republican part clownshow and abortion issues and there's a lot more potential mobilizaton from the Dem side.