I guess they very occasionally do, and in that case, I would be somewhat more wary about voting for someone with this fabled 70%-chance-of-being-a-sociopath DNA test even if they otherwise had given me no particular cause for alarm. We're not talking about a very common situation here, though.
Don't the names Hitler, Stalin, Mao, Kim Il-sung and Pol Pot cause you to think that something about power attracts the wrong kind of people.
I wrote an article for h+ predicting that the rapid fall in the cost of gene sequencing will allow U.S. voters to learn much about presidential candidates' DNA. The candidates won't be able to stop this because:
DNA analysis has a decent chance of reducing political bias by providing objective information about candidates. If, for example, 70% of the variation in human intelligence is determined by identified genes then DNA analysis would reduce disagreements among informed voters over a candidate's intelligence.