For example, if you are a US presidential candidate, what tactics would you use to invisibly switch voters' choice to you?

I vaguely remember that when a president becomes very widely accepted as a good or bad president, many people will misremember that they voted for or against him respectively; e.g. much fewer people would admit (even to themselves) having voted for Nixon than the actual number that voted for him. If this is so, then maybe the answer is simply "Win, and be a good president".