Swings in the stock market are foretelling moves in presidential polls, according to Tom McClellan, technical analyst and editor of the newsletter The McClellan Market Report. If you want to know who will pull ahead in the 2016 election, he said, look to equities.

"The stock market movements tend to lead the changes in the poll numbers by about a week," McClellan told CNBC's "Squawk on the Street" on Wednesday. "If you see a movement in the Dow or the S&P or your favorite index, you're likely to see the same movement show up about a week or a week and a half later in the poll numbers."

McClellan compared major U.S. indexes and polls from RealClearPolitics, and found that the two move in lockstep. He started comparing them in the 2000 election, and found that numbers become accurate when daily polling begins closer to November.

Former Secretary of State Hillary Clinton became the presumptive Democratic presidential nominee Tuesday night. McClellan pointed to the corresponding Dow Jones industrial average, which has moved higher in the past two weeks as Clinton gained ground.

"If the market moves up, that tends to benefit the incumbent in the last elections," McClellan said, adding that Clinton, the way the model works, is being viewed by the market as the incumbent.

"If the market bids up people tend to feel better about it, and if people are feeling good they like the guy who's in office more."