Past voting records aren’t going to play a part in this upcoming election because many people I know, who have voted D the last few years are switching to Trump this time. Everything is out the window as far as predictions and past voting patterns.
You are correct, past voting patterns will be different relative to who they vote for. However, these are the people that will probably vote in the next election. When your group selection is only done by e mail, it automatically becomes bad data as it increases the number of people in the sample that did not vote in the past and are more likely to not vote in the future.