Amid relentless debate about whether at 80 Joe Biden is too old to be president or to complete an effective second term, an eagerly awaited book on his time in the White House reports that Biden has privately admitted to feeling “tired”, even as it describes his vast political experience as a vital asset. “His advanced years were a hindrance, depriving him of the energy to cast a robust public presence or the ability to easily conjure a name,” Franklin Foer writes in The Last Politician: Inside Joe Biden’s White House and the Struggle for America’s Future. “It was striking that he took so few morning meetings or presided over so few public events before 10am. His public persona reflected physical decline and time’s dulling of mental faculties that no pill or exercise regime can resist. “In private, he would occasionally admit that he felt tired.” Foer does not cite a source for Biden’s reported private remarks but his book, according to its publisher, Penguin Random House, is based on “unparalleled access to the tight inner circle of advisers who have surrounded Biden for decades”. The Last Politician will be published in the US next week. On Tuesday, as the Atlantic published an excerpt on the withdrawal from Afghanistan, Politico noted tight security around the release and anxiety in the White House. The Guardian obtained a copy. Biden’s age has been a constant of coverage since the former senator and vice-president entered the race to face Donald Trump in 2020. At 77, Biden beat Trump convincingly and became the oldest president ever elected. If Biden wins a second term next year, and completes four years in power, he will be 86 when he steps down. Republican candidates to face Biden have relentlessly focused on his age, with rightwing pundits piling in – despite the fact the clear Republican frontrunner, Trump, is 77 years old himself. But public polling has long showed concern about Biden’s age among Democratic voters. This week, the Associated Press and the Norc Center for Public Affairs showed 77% of respondents (89% of Republicans and 69% of Democrats) saying Biden was too old to be effective if re-elected. In the same poll, only 51% (and just 29% of Republicans) said Trump’s age would be a problem if he returned to the Oval Office. Foer, a former editor of the New Republic, a progressive magazine, does not shy from the issue. But he does stress how Biden’s massive political experience – he won his US Senate seat in Delaware in 1972, chaired the Senate judiciary and foreign relations committees and was vice-president to Barack Obama from 2009 to 2017 – has given him unique strengths in the White House. Citing the Inflation Reduction Act and other attempts to address the climate crisis, Foer says Biden is not guilty of governing in the short term “because [he] will only inhabit the short term”, a failing of older politicians. In something of a backhanded compliment, Foer writes that Biden has sometimes muffed public remarks not because of the challenges of age, but because of “indiscipline and indecision” seen throughout his career. In the same passage in which he reports Biden’s admission to being tired, meanwhile, Foer says the president’s “wartime leadership”, regarding supporting Ukraine in its fight against the invading Russian army, “drew on his weathered instincts and his robust self-confidence”. Regarding Ukraine, Foer writes, “the advantages of having an older president were on display. He wasn’t just a leader of the coalition, he was the West’s father figure, whom foreign leaders could call for advice and look to for assurance. “It was his calming presence and his strategic clarity that helped lead the alliance to such an aggressive stance, which stymied authoritarianism on its front lines. “He was a man for his age.”