Wives, familiar with their husbands’ limitations, are known to prompt them from time to time. So, it was no surprise when Bill Biden muttered 'Trump' under her breath after 'Sleepy' Joe Biden monetarily forgot the name of the US President while participating in a virtual rally. Not just that, the aspirant to White House seemed to be caught in a time warp.

‘‘We need to stop four more years of George,’’ declared Biden, in all seriousness. The online audience was soon wondering: But did he mean Bush senior or junior?

Many speculated that he was thinking of George W. Bush, president from 2001-09, but he may also have been thinking of George H.W. who was in office from 1989-93. The faux pas will once again raise doubts about the 77-year-old's mental agility - a topic President Donald Trump has harped upon in the run-up to the election.

Earlier on Sunday, Biden, in an interview with 60 Minutes, laughed off Trump's attacks on his mental capacity. ‘‘Hey, the same guy who thought that the 911 attack was a 7-Eleven attack?’’ Biden responded. He insisted it was Trump - not him - who was losing his grip.

Hours later President Trump blasted Biden, tweeting: ‘‘Joe Biden called me George yesterday. Couldn't remember my name. Got some help from the anchor to get him through the interview. The Fake News Cartel is working overtime to cover it up!’’

‘‘Who's the president?' This is the question a doctor would usually ask if you had a bang on the head,’’ added Trump. The President has often joked about Biden ending up in a care home during his tenure and the office being taken over by his running-mate Kamala Harris.