Election prediction markets were the first to call the second presidential debate. Who did investors say won? Trump, but by the slimmest of margins.

Donald Trump won the second presidential debate, but only by the smallest of margins, according to election prediction markets. These markets, which are a reflection of how active traders feel on a number of campaign issues, moved throughout the debate, sometimes in Hillary Clinton's favor, sometimes for Trump, but settled on Trump improving his chances of winning the election to about 23%, up from about 19%.

Watch as TheStreet politics editor Jeremy Greenfield and politics reporter Emily Stewart talk with John Aristotle Phillips, CEO of PredictIt, the largest prediction market in the U.S., to break down the numbers around the second presidential debate.

This article was written by a staff member of TheStreet.