While Intrade has betting markets on the US presidential election, they are unregulated and of questionable US legality. Nadex went through the expensive legal hoops to apply for permission to run a regulated market. Last week:

The CFTC determined that the contracts involve gaming and are contrary to the public interest. (more)

Why?

It could unduly influence election results. … the contracts could run afoul of the election process if traders had financial incentives to vote for particular candidates. (more)

They still allow election betting at the Iowa Electronic Markets, where stakes are limited to $500. They still let people work for campaigns and administrations, which gives them financial incentives to vote for certain candidates. And they let candidates take positions favoring some industries, occupations, and locations, over others, which gives people financial incentives to vote for and against candidates.

We also let people tell other people which candidates they favor, which gives people non-financial incentives to vote for those candidates later. And since every bet for a candidate is matched with a bet against that candidate, whenever a betting market gives anyone a financial incentive to vote for a candidate, it at the same time gives someone else a financial incentive to vote against that candidate. Why are all the rest of these “due” influences, while bets are “undue” influences?

Paula Dwyer argues:

Naked credit default swaps on Greek sovereign debt (buying a CDS without owning the underlying debt) are no more than a bet on a Greek default. Will the CFTC be barring them, too? (more)

Law and Economics professors Eric Posner and Glen Weyl support the CFTC:

Financial instruments that serve primarily as a means of speculation rather than hedging should be banned … Suppose that two individuals, neither of whom uses or produces oil, harbor different opinions about the future price of oil and decide to wager on it. Both parties willingly participate, because they think they’re each getting the best of their confused counterparty. Clearly, both of them cannot gain from this transaction, and the wager itself creates rather than reduces risk. While each party thinks it is getting the better of the other, both agree that on average both of them will be worse off because on average they will win and lose on the same number of bets, and both of their incomes will be less smooth and predictable on account of their wagering. As a consequence, this sort of speculation is socially harmful. …

In controlled and appropriate contexts, [gambling] can be a source of entertainment for people who are aware of and willing to accept the potential losses. But participants in financial markets are usually seeking financial security rather than entertainment, and they typically have little sense of the risks they are taking on. … A second potential benefit of allowing trading in derivatives is the information that they provide to market participants. The knowledge of the likely outcome of the presidential election provided by the wisdom of the crowds is useful for planning by businesses, individuals, and governments. But that information is only valuable to the extent that it enables real economic decisions to be made more effectively.

Consider: why should we let people argue on elections? Similar to the above, one could say:

People mainly argue in the hope of winning arguments, thinking that they are taking advantage of confused opponents. While each side hopes that further events and discussions will reveal them to have been more in the right, both sides understand that this can’t happen for both of them. Yes, people might argue just to have fun, but election pundits seem serious – wanting more to prove the other side wrong. And most people who argue politics seem to have little understanding of what they are talking about. Yes, arguments can produce useful info for others, but the value of the info produced in election arguments is small compared to the time lost arguing. Thus we should ban arguments on elections.

Election arguers and bettors both seem motivated by a similar mix of enjoying the process and hoping to win. But the info produced by bettors is far more persuasive, reliable, and useful – you have far better reasons to believe betting market odds than whatever the apparent winner of a political argument has claimed.

You might counter that people sometimes argue about who should win an election, rather than who will win. But betting markets can collect info on that topic as well – we can bet on outcomes after the election conditional on who wins the election. These sort of markets would be enormously helpful to tell voters about which candidate will best promote health, peace, or prosperity. Yet such markets are now banned because they might “unduly” influence elections, or let people “waste” their time “arguing” about elections. Heaven forbid we should waste time figuring out which candidate would actually help us more.