Joseph R. Biden Jr. and the Democratic Party could raise almost $1 million every single day between now and November, and he would still barely catch up to what President Trump and the Republican Party had in the bank at the start of April — let alone what Mr. Trump will have by Election Day.

New fund-raising figures released late Monday show the depth of the financial hole in which Mr. Biden finds himself at the start of the general election campaign: The presumptive Democratic nominee and his party are nearly $187 million behind the Republican National Committee and Mr. Trump, who has spent the last three years stockpiling his huge war chest.

The sheer size of Mr. Trump’s early advantage creates a unique set of financial and political pressures for Mr. Biden. He must find ways to both expand his appeal to small online contributors and attract huge seven- and eight-figure checks to the outside super PACs supporting him — all while sheltered in his Delaware home because of the coronavirus.

To lure the money that he will need to compete effectively in battleground states, Mr. Biden will have to navigate a series of consequential political decisions, refining his message, honing his policy agenda and selecting his running mate. But Democratic strategists say he has at least one point in his favor: He has wrapped up the nomination and started uniting the party relatively early in 2020, giving focus to the party activists and leading financial patrons who are singularly obsessed with defeating Mr. Trump.