Former Vice President Joe Biden conceded in an interview released Tuesday that he cannot say for certain whether he would have defeated President Donald Trump in the 2016 election.

“I don’t know,” the 2020 Democrat presidential frontrunner told the New York Times in June. “Everybody says that. But look, I don’t know. You’ve got to be in the game. I thought Hillary would have made a good president.”

Biden was floated as a potential White House hopeful as the Obama administration drew to a close, though he ultimately opted against running and endorsed Democratic presidential nominee Hillary Clinton. President Trump went on to beat Clinton 304 to 227 in electoral college votes in 2016.

Biden cited him the death of his son, Beau Biden, for deciding against seeking the highest office in the land. Beau died of brain cancer on May 2015 at 46 years old.

Despite a drop in the polls, Biden still leads the field of 2020 Democrat field in all early state, a series of surveys show. The former vice president will face off against Sen. Kamala Harris (D-CA) in next week’s second presidential debate after a dismal first debate performance in which he struggled to defend his position on busing.

Appearing last July on CBS News, President Trump said President Barack Obama took Biden “out of the garbage heap” and that running against him in a general election contest would be “a dream.”

“I dream about Biden, that’s a dream Look, Joe Biden ran three times, he never got more than 1% and President Obama took him out of the garbage heap and everybody was shocked that he did. I’d love to have it be Biden,” he said. “Biden, never by himself, could never do anything.”