Joe Biden is continuing to insist on staying in the presidential race, despite escalating calls for him to end his re-election campaign. 

Four more Democrats currently in Congress have voiced their belief that Biden needs to step down during a recent phone call.

US correspondent Dan Mitchinson says it's unclear who could replace Biden at this point in the campaign. 

"You have the other Democrats who are saying - okay, that would mean Kamala Harris would have to step up and slide into the role vacated by Biden. But she just doesn't have the it-factor."

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