Joe Biden could be axed as the Democrat candidate as late as August amid growing concerns for his mental fitness.
As the latest polls remain tight, senior democrats suggest they will delay their strike as late as possible to slam hopes of a second term.
The formal nomination is set to take place in Chicago on August 19.
Democrat operatives in Washington DC say the late hit will not only stop Biden from becoming president again but also aims to maximise the Democrats’ chances of keeping control of the Senate in November, The Sun reports.
Biden's mental fitness has been questioned following the release of a Department of Justice report which claimed that the president has "diminished faculties" and a "poor memory".
The report, authored by Special Counsel Robert Hur, who spoke with the President regarding classified documents, described the 81-year-old as a "well-meaning, elderly man."
Despite no democratic challengers yet standing forward for the role, Vice President Kamala Harris is dropping hints she is ready to lead.
Other possible names include Michigan Governor Gretchen Whitmer, California Governor and Gavin Newsom.
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An overwhelming majority of voters remain worried about his age, a new poll by Quinnipiac University showed.
The poll, conducted from February 15 to February 19, found that 67 per cent of voters said the 81-year-old president is too old to effectively serve another term.
Top Democrat Chuck Schumer dismissed reports that his memory was subpar as simply Republican "propaganda".
Republicans have called for the recordings of Biden’s interviews with Hur to be released.
The White House previously said Hur’s comments on the President’s memory were "gratuitous" and "inappropriate".
Responding to questions about his age, Biden said: "I am well-meaning. And I’m an elderly man. And I know what the hell I’m doing.
"I’ve been president – I put this country back on its feet. I don’t need his recommendation."
Biden and Trump will likely go head to head in this year's US Presidential Election later this year on November 5.
