Joe Biden pushed back against those doubting his fitness for office in the wake of a string of recent gaffes by claiming he is not “going nuts.”

“I want to be clear; I’m not going nuts,” the 76-year-old former vice president told an audience in New Hampshire on Friday after being unable to recollect a speech he gave at Dartmouth College only hours prior. “I’m not sure whether it was the medical school or where the hell I spoke. But it was on the campus.”

The defense comes as Biden has worried even his staunchest allies for often confusing times and places on the campaign. Last week, while addressing voters in Iowa, Biden mistakingly claimed that Martin Luther King Jr. and Robert F. Kennedy were assassinated during the late 1970s.

“Just like in my generation, when I got out of school, when Bobby Kennedy and Dr. King had been assassinated in the ’70s — the late ’70s — I got engaged,” Biden told the audience, before proceeding to ramble about the counter-culture movement of the 1960s.

The statement was quickly called out as false, as both men were assassinated within mere months of each other in 1968 — a turbulent year in American history. The confusion was especially troubling for Biden, who has often cited both men as big influences on his decision to enter politics. Biden was supposedly so taken with Kennedy, whom he once called “the one true hero of my life,” that he plagiarized substantially from his fallen hero during the 1980s.

Biden was similarly fuzzy earlier this month when discussing with reporters in Iowa his proposal for gun control.

“Those kids in Parkland came up to see me when I was vice president,” said the former vice president, before claiming that when the survivors visited Congress, lawmakers were “basically cowering, not wanting to see them. They did not want to face it on camera.”

Many pointed out that the tragic shooting at Marjory Stoneman Douglas High School, which resulted in 17 fatalities and over a dozen injuries, occurred on February 14, 2018, more than a year after Biden left office.

Apart from having trouble with dates, Biden has also tripped over his words during speaking engagements and appeared confused about his whereabouts. This month, when discussing a recent speech in which he accused President Donald Trump of fanning “the flames of white supremacy,” Biden mistakenly claimed it took place in Burlington, Vermont, rather than Burlington, Iowa. He made a similar mixup over the weekend during a campaign stop in New Hampshire.

“I love this place. Look, what’s not to like about Vermont in terms of the beauty of it?” Biden said while standing in front of Lindy’s Diner in Keene, New Hampshire.

Such gaffes and questionable statements have reignited doubts from many on the left regarding Biden’s fitness for the presidency. Jamil Smith, a senior writer for Rolling Stone magazine, summed up the pervading sentiment on the left when he called on Biden’s campaign to “step forward” and explain “what is going on with him” after the former vice president’s Parkland blunder:

There is no explanation that makes @JoeBiden look good. Still, the campaign needs to come out and say what is going on with him. Apparently, this wasn’t the only time today that he said that he was VP during the Parkland attack—in 2018. You don’t say that. https://t.co/mj3hopFLuI — Jamil Smith (@JamilSmith) August 10, 2019

Biden’s own allies have been more muted in their criticism, suggesting the candidate’s team cut down on his public appearances, especially in the evenings, when he is known to make gaffes.