CNBC reports that a former White House trade official said that markets need to pay attention to the “high risk” of a disputed U.S. presidential election outcome as dynamics shift ahead of the vote.

Such an election outcome could happen if a candidate deemed to have lost refuses to concede, or if he questions the legitimacy of the results. 

“I think it’s a high risk and I do think markets need to pay attention to it. I’ve detected a real shift in the election dynamics in the last six to eight weeks,” Clete Willems, a former deputy director of the National Economic Council, told.

“In early August, I think the president ... felt like he was behind, I think right now he feels like he has the wind at his back for a couple of different reasons,” he said.

Willems explained that there’s a general perception that the U.S. economy is improving and the president has “done well in some of the law and order issues” — and that likely works in Trump’s favor.