Though more than two years have passed since the presidential election, former FBI Director James Comey said he remains troubled by his potential role in the rise of Donald Trump, questioning the impact of the bureau’s investigation into Hillary Clinton’s emails.

In October 2016, just one month before Election Day, Comey reopened a probe into then-candidate Clinton’s use of a private server to conduct government business when she was secretary of state, meaning she may have violated security regulations. The scandal tarnished her reputation and indelibly marked her campaign.

Critics of the investigation argue it was a tipping point in the election, swinging it in Trump’s favor. Asked by CNN’s Christian Amanpour whether he’s kept awake at night by that possibility, Comey replied, “Sure.”

“I hope someday somebody proves that what we did was irrelevant,” he said.

The investigation was launched in July 2015 and appeared to end with Comey’s announcement a year later that he recommended no criminal charges against Clinton, since no evidence was found to indicate her mishandling of classified information was intentional. However, the discovery of additional emails led to the probe’s resumption.

Two days before the election, Comey announced that the FBI stood by its previous conclusion that Clinton committed no criminal acts.

“I hope we had no impact ... but all it does is increase the pain,” he told Amanpour. “It doesn’t change how I think about the decision.”

“My view and the view of my team was we cannot conceal from the American people that the investigation we told them and fought to tell them is done, is done, is done, is not done, and the result could change. We just couldn’t do that.”