>The underlying assumption of such markets is that no player has more than one vote in the actual election, out of some 150 million or so votes, so each individual player's ability to affect the outcome is negligible.
But this is not necessarily true. In the extreme case, a bettor could be one of nine Supreme Court justices. Or a participant in some sort of fantasy vote-rigging conspiracy. Or even a political insider tanking their candidate's own chances and betting against themselves. There's a pretty wide range of people who could plausibly (or not-so-plausibly in the conspiracy example) have more than a one-vote influence over the result of the election.
But this is not necessarily true. In the extreme case, a bettor could be one of nine Supreme Court justices. Or a participant in some sort of fantasy vote-rigging conspiracy. Or even a political insider tanking their candidate's own chances and betting against themselves. There's a pretty wide range of people who could plausibly (or not-so-plausibly in the conspiracy example) have more than a one-vote influence over the result of the election.