Baku, March 27, AZERTAC

As the election approaches, President Biden is making regular calls to former President Barack Obama to catch up on the race or to talk about family. But Mr. Obama is making calls of his own to Jeffrey D. Zients, the White House chief of staff, and to top aides at the Biden campaign to strategize and relay advice, according to New York Times.

This level of engagement illustrates Mr. Obama’s support for Mr. Biden, but also what one of his senior aides characterized as Mr. Obama’s grave concern that Mr. Biden could lose to former President Donald J. Trump. The aide, who was not authorized to speak publicly, said that Mr. Obama has “always” been worried about a Biden loss. And so, the aide added, he is prepared to “eke it out” alongside his former vice president in an election that could come down to slim margins in a handful of states.

Perhaps for the first time, the two are on the same page about Mr. Biden’s future. In a sign of things to come, they are to appear together, with former President Bill Clinton, at a major fund-raiser for the Biden campaign at Radio City Music Hall in New York on Thursday.

In 2015, as Mr. Biden was grieving the loss of his eldest son, Beau, and contemplating running for the presidency, it was Mr. Obama who gently suggested that it was not his time. In a memoir, “Promise Me, Dad,” Mr. Biden wrote that Mr. Obama told him that if he “could appoint anyone to be president for the next eight years,” it would have been Mr. Biden. The vice president wrote that “the mere possibility of a presidential campaign, which Beau wanted, gave us purpose and hope — a way to defy the fates.”

But after discussing the stakes with Mr. Obama, he took himself out of contention and stepped aside for Hillary Clinton, seen by the Obama White House as the far stronger candidate. The decision bred distrust and lasting resentment among some of Mr. Biden’s aides. Several of them work in the White House today, and they believe that Mr. Obama and his advisers sidelined Mr. Biden, whom they think could have changed the course of history and beaten Mr. Trump in 2016.

In 2019, when Mr. Biden entered the race against then-President Trump, Mr. Obama withheld his endorsement until after the Democratic primary, though he privately worked to clear a path for Mr. Biden. He also gave his blessing for the Biden campaign to use their interactions in the Obama White House in campaign materials, including footage of when Mr. Obama surprised his vice president with the Presidential Medal of Freedom shortly before leaving office.

In the 16 years since their first campaign together, the relationship has been defined by its odd-couple characteristics: The Harvard-trained professor and the guy from Scranton. The Senate Foreign Relations Committee chairman who went on to serve a former junior member. The cool head and the Irish temper.

It took Mr. Obama time to warm to Mr. Biden, who was brought on as the Washington elder to help the exciting but inexperienced young president-to-be. Mr. Biden struggled with being second-in-command from the moment he joined the ticket.

Over time the two jelled, with Mr. Biden leveraging his relationships on Capitol Hill to help steer a massive stimulus package through Congress in the Great Recession and to push the Affordable Care Act over the finish line. He famously congratulated Mr. Obama as the president signed the health bill into law, whispering “Mr. President, this is a big deal” with an inserted adjective not suited for national television.

The two were not aligned on everything. Mr. Biden was vehemently against Mr. Obama’s decision to send more American troops to Afghanistan in 2009, a disagreement that would become a focal point for Robert K. Hur, the special counsel who investigated the president’s handling of classified documents. A classified and handwritten document memo Mr. Biden sent to Mr. Obama on Afghanistan had been found at Mr. Biden’s residence in Delaware by investigators.

In a lengthy interview last October with Mr. Hur, Mr. Biden hinted at their opposites-attract dynamic during a portion of the discussion that was meant to probe how often and in what manner he spoke with other senators about sensitive matters, including the Iran nuclear deal.