Democratic presidential nominee Joe Biden seemed to have confused Donald Trump with former president George W. Bush during an online fundraising event on Sunday.

Sitting next to his wife Jill Biden, Joe Biden addressed his supporters online during the “I Will Vote” virtual concert and noted that he was fighting against “four more years of George.” “The character of the country, in my view, is literally on the ballot,” he said. “Four more years of George, er George, er, he—we’re going to find ourselves in a position where, if Trump gets elected, we’re going to be in a different world,” he added.

His wife then appeared to remind him who the current president was, telling him, “Trump.” People on social media were quick to speculate that Joe Biden was thinking of former U.S. president George W. Bush, who led the nation from 2001 to 2009, when he tried to refer to Trump. During his term, Biden was a senator for Delaware and was on the presidential ticket with former president Barack Obama.

Meanwhile, the blunder once again raised doubts about the mental agility of the 77-year-old presidential candidate. Following the online event, Joe Biden’s mistake drew criticisms on Twitter, with people questioning whether Joe Biden was mentally fit enough to assume the presidency.

“Watch his wife saying Trump under her breath 3 times,” one social media user wrote. “The look on Jill’s face was like, ‘come one Joe, get the train back on the tracks,’” another wrote.

Some social media users also claimed that Joe Biden was showing signs of dementia, something that Trump has long accused his rival of having. One user named Karen Gresham said she recognized signs of dementia after watching Jill, not Biden.

“Having been charged with the care of a relative with dementia, I recognize the actions of Jill,” she wrote. “Saying the words he can’t find. Moving him to the place he’s supposed to stand. Guiding his steps when he is unsure of his destination. You don’t have to watch him. Watch her,” she added.

On Sunday, Biden laughed off Trump’s attacks on his mental agility. “All I can say to the American people is watch me, is see what I’ve done, is see what I’m going to do. Look at me. Compare our physical and mental acuity,” he said. 

Vice President Joe Biden U. S. Vice President Joseph Biden speaks during a memorial service for the late former Israeli president Shimon Peres at the Adas Israel Congregation October 6, 2016 in Washington, DC. Getty Images