I submit that this is actually a testable proposition. Sample 100 people from a country where English is taught well, but the political system is so different from the US that people are unlikely to have tribal predispositions to favor Democrats or Republicans (100 Singaporeans, maybe). Show them the Palin-Biden debate, and a couple of examples of each of them speaking impromptu. Then ask the respondents whom they think is more intelligent. How substantial a sum would you be willing to wager that Palin would win such a poll?
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.