Allies of Mr. Trump believe there is virtually no chance that he can win the popular vote, and they have seen some states on his victorious 2016 map shift markedly away from them. They are particularly pessimistic about Michigan, which Mr. Trump narrowly won four years ago, and are looking to flip Nevada, which has many white voters without college degrees, and especially Minnesota, the state he lost by the closest margin four years ago and the site of weeks of unrest following the police killing of George Floyd.
“There is no question that Joe Biden has to earn Minnesotans’ votes, that he has to explain why the chaos of today is going to be replaced with the calm he is proposing,” said Representative Dean Phillips, a Democrat who in 2018 captured a historically Republican seat in the suburbs.
Mr. Phillips said he had shared that view with the Biden campaign and expected the former vice president to visit his state soon.
Yet even as Mr. Trump attempts to win over states that were once reliably blue, he is also imperiled in traditionally red-tinted states that have been hit hard by the pandemic, like Florida and Arizona. A Trump strategy that is aimed at driving racial polarization in the Midwest could backfire in more heterogeneous states in the South and West.
With those dynamics in mind, at least two pro-Biden groups have approached Michael R. Bloomberg, the billionaire former presidential candidate, about the possibility of funding an enormous blitz against Mr. Trump in Florida, arguing that delivering the state’s 29 Electoral College votes to Mr. Biden would effectively end the election. Mr. Trump’s weakness with older voters has made him acutely vulnerable in a state where affluent retirees have been a cornerstone of the Republican coalition.
But aides to Mr. Bloomberg have so far demurred, explaining that the former New York City mayor has not approved any plans for spending money in the presidential race, people involved in the conversation said.
Still, the possibility of a knockout in the Sun Belt is enticing to Democrats, particularly as surveys from both parties continue to show Mr. Trump at risk in red-tinted states like Georgia. Sam Park, a Georgia Democratic state legislator who spoke at Mr. Biden’s convention, said the campaign had signaled that it planned to contest the state seriously in the final two months of the race, the first time a Democrat has done so this century.