DoubleLine's Jeffrey Gundlach says December hike is a huge 'who knows?'

Bond guru Jeffrey Gundlach said that there is a lot of uncertainty ahead of a potential interest rate hike in December.

Three presidential debates and an election will take place before the Federal Reserve's December meeting, the chief executive of DoubleLine Capital said in an exclusive interview with CNBC's "Fast Money" on Wednesday.

"I think December is a huge 'who knows?'" Gundlach said.

Gundlach said he's looking for "downside volatility to develop," which may happen if GOP nominee Donald Trump gains momentum and some ground in the polls after the Sept. 26 presidential debate. He said the view that the New York businessman may win the election has led to fear that "the world is going to come to an end."

Gundlach explained, however, that the number of dissenters in Wednesday's Fed meeting "shows that there is a growing mood at the Fed that at some point they have to follow through with these interest rate increases."

Three members from the hawkish Fed bloc — Esther George, Loretta Mester and Eric Rosengren — dissented from the central bank's statement, an unusual split considering Chair Janet Yellen's adeptness at keeping the committee united. It was the most "no" votes since the December 2014 meeting.

The Fed left its benchmark federal funds rate unchanged on Wednesday. The U.S. central bank also lowered its year-end and 2017 forecasts.

What investors should be looking at more globally is the potential for central banks to switch tactics, Gundlach said.

"There's a growing awareness in Europe and Japan and I think indeed in the United States that these policies have not generated the results that they were designed to generate," he said.

Gundlach said that just a couple days ago, investors seemed to be hung up on the Bank of Japan's meeting, but the policy changes it announced did not move markets as much as some had anticipated.

"But something interesting did happen at the BOJ and that is they sort of admitted that they're not getting the results that they're hoping for from negative interest rates and indeed they might want to steepen out their yield curve and get to positive interest rates," he said.

Gundlach argued that the bond market may be "sniffing out a pivot to fiscal stimulus," which would change the game.

"You would get a different kind of mentality about policy and interest rates," said Gundlach.

He said that there are pockets of momentum in the stock market right now. Gundlach, whose firm has more than $100 billion in assets under management, said he's shorting consumer discretionary stocks in the current environment. He explained that while that sector has risen in recent years, it's a "bad story" right now to invest in.

While Gundlach declined to name individual companies he has short positions in, the DoubleLine chief executive said he is shorting some restaurant, retail and airline stocks.

— CNBC's Jeff Cox contributed to this report.