After a rough week of campaigning, that started with him being caught plagiarizing a 2020 climate plan and saw him rescinding his decades-long support for the amendment banning federal funding for abortion, Biden has resorted to a tried and trusted means of boosting his profile – referencing former US President Barack Obama.

"Happy Best Friends Day to my friend, Barack Obama," Biden tweeted on Saturday, complete with a photo of a pair of craft friendship bracelets with the names "Joe" and "Barack".

Those are real, having first surfaced at the height of the Biden-Obama 'bromance' in 2016, when then-President Obama filmed posted a video of himself making one of them, and then-VP Biden tweeted a photo of the pair to congratulate Obama with his 55th birthday. He used the same photo on Saturday.

Having inspired jokes in the past, now the reminder looks like a timely insurance move so the voters don't forget why they like Biden so much.

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Although Biden leads the packed Democratic field by double-digits, with 31 percent against Bernie Sanders' 14 percent in the latest Ipsos poll, his positions have been shaken by his flip-flop on the Hyde Amendment made under pressure from fellow liberals. The turnaround has even prompted former Obama strategist David Axelrod to question Biden's resolve. "So, that was a flip-flop-flip which is never a good thing in politics and it raises questions about his own performance and his own steadiness and his campaign's performance," he said.  

While some Biden and Obama supporters fawned over the cutesy display of their friendship, others have ridiculed 76-year-old Biden for using it as his main source of political credit.

"Dude is 70-whatever years old and his campaign pitch is mostly "I'm totally BFFs with that guy you like," a commentator wrote.