> But all along, this person's preference is Democrat > Republican > Independent. That's a great point, thank you. I should have tried to describe a more subt

> But all along, this person's preference is Democrat > Republican > Independent. That's a great point, thank you. I should have tried to describe a more subtle effect where someone sees the policies of the far left candidate and it taints their view of the Democrats, who they now view with suspicion, fearing the Democrats might secretly support the same extreme policies. Alternatively, a Republican voter might see the Overton window shift and consider the Democrats a more centrist party, and so drop their support for the Republicans. The problem is, these parties (and candidates) aren't spherical cows in a vacuum, and neither are voters. Voters have imperfect information and have to try to make predictions about which politicians are lying, and what direction the mood of the country is moving; so the addition of another party into an electoral contest can quite reasonably cause someone to change how they view the existing parties and even flip their support.