However, it is not the overwhelming approval that many new presidents have had, a reflection of widely divided times. From Dwight D. Eisenhower to George Bush, every newly elected president was in the first six months of their 60s or 70s, according to figures from poll website FiveThirtyEight. However, Bill Clinton averaged just 50.5 percent and George W. Bush only 53.9 percent. Mr Obama was up at 60.2 percent, but Mr Trump averaged 41.4 percent, the lowest of all presidents in election history.

The question is how long can Mr. Biden hold on to Americans who backed him out of opposition to Mr. Trump, not out of conformity with his ideology, especially the so-called Never Trump Republicans, many of whom still favor conservative policies.

“I’m sure Biden will do something at some point that I disagree with, but right now their focus on Covid is important and appropriate,” said Rick Wilson, a longtime Republican agent who helped found the Lincoln Project that defeated Mr. Trump. “He’s hit the hard edge of a Trump-controlled party and I suspect the GOP’s honeymoon was over before it started.”

To prepare for the enormous challenges he had inherited, Mr. Biden and his team studied books on Roosevelt such as Jean Edward Smith’s “FDR” and Jonathan Alter’s “The Defining Moment” as well as other classics such as Arthur M. Schlesinger Jr.’s ” A Thousand Days “of John F. Kennedy’s abbreviated presidency. Mr. Biden has also consulted regularly with historian Jon Meacham, who helped write his inaugural address.

Roosevelt took office after three years of economic disaster in 1933 and responded with a series of laws that changed America and the role of government in society, even if they did not completely end the Great Depression. Mr Biden’s executive actions are less permanent as they can be reversed by future presidents. But they mimick Roosevelt’s desire for determined energy.

“Biden’s executive orders will be more permanent than Obama’s and more in line with much of what Roosevelt did early on,” Alter said in an interview. If the government can vaccinate more than 100 million people against the coronavirus in the first 100 days, Mr Biden has mobilized a response to the pandemic even faster than Roosevelt’s early New Deal programs responded to the Depression.

“Biden’s mobilization will dwarf this, and when he is in control of the virus at the end of his first 100 days, he will prepare for all sorts of other accomplishments,” said Alter.