evidence: Donors have urged Mr Biden to step aside, suggesting California’s Gavin Newsom and Michigan governor Gretchen Whitmer as potential replacements amid rising panic about the future of the campaign. Mr Biden repeatedly struggled to express himself during the debate with Donald Trump, producing rambling and incoherent answers. [...] Strategists working for at least three separate Democrats said they have received texts from party donors asking them if their candidate would step forward to replace Biden as the presidential nominee.