With Donald Trump drawing enthusiastic crowds everywhere he goes, and steadily increasing his percentage share of the polls week after week no matter how many gaffes he makes, it's starting to seem like nothing can stop the blustering magnate's march to the GOP nomination.

But it's also entirely possible that future historians will look back on this as a time of temporary madness — the tail end of the summer of Trump — and that cooler heads will prevail by the time we're trudging through the snow to the Iowa caucuses. Who can say?

Answer: the free market.

Spoiler alert: Seeing the future is impossible until someone invents a time machine, or unless you're willing to overlook a large number of bad predictions in favor of one or two good ones. But there is one mechanism that has been shown to be surprisingly accurate, especially when it comes to presidential elections: prediction markets.

The idea behind prediction markets is that investors put their money where their mouth is. You buy shares in one possible future or another, and the price of the shares changes according to their popularity. It's essentially the same as futures trading; you're just dealing with less tangible assets. The rising and lowering of share prices gives you a clue as to where a given event is headed.

Numerous research papers have found that political prediction markets such as the Iowa Electronic Market, introduced by the University of Iowa back in 1988, are more accurate when it comes to calling the winners than the volatile polls. In 2008, the IEM predicted Barack Obama would be the eventual Democratic nominee as early as January.

People are bad at prediction individually; in the aggregate, it turns out, they're actually pretty good.

So what does this mean for Trump's chances? It means they're not good. PredictIt, one of the largest prediction markets currently running (it's operated as a nonprofit by Victoria University in New Zealand, which is how it gets around gambling regulations), is currently selling Trump shares for around 24 cents on the dollar at time of writing.

That means you can get a share in Trump's GOP nomination victory, a share that will pay out a dollar if Trump wins, for just 24 cents. You'd think those were good odds, but more people currently want shares in a Jeb Bush victory (around 38 cents a share) and even a Marco Rubio victory (25 cents a share) than believe in Trump.

About a million people have participated in the PredictIt GOP nomination market so far. And while Trump's poll numbers have been going up all month, they've actually been dropping on PredictIt:

Image: PredictIt

Not great news for Trump, considering the site boasts an 89% accuracy rate so far — that is, 89% of the events its markets opted for in the run-up to an event came to pass. For example, PredictIt traders correctly saw the outcome of the recent Greek financial referendum when most pundits didn't.

"When the market diverges from 'consensus expert opinion' or public opinion polling, it’s the markets that are right in the end," says John Aristotle Phillips, CEO of Aristotle, a company which provides technical support for PredictIt. "I would not bet against PredictIt traders in the aggregate."

And it isn't just this one market that thinks Trump is a loser. PredictWise, an aggregator of other prediction markets and betting shops run by members of Microsoft Research, has Jeb Bush at a 38% chance to win the nomination — while Trump comes in second with a measly 16%.

Could the Donald still win? He's certainly shown a propensity for upending all other expectations, and prediction markets aren't infallible. He probably won't even mind finding one area where he is still actually an underdog.

Then again, Trump has bet against the market one or two times before in his career — and had to declare corporate bankruptcy as a result.

We'll find out soon enough if the prediction markets pass their next test relating to Trump: PredictIt traders are currently saying he'll get the biggest drop in polling after Wednesday's debate.