Joe Biden's half-century in politics has been an exercise in overcoming adversity.

From the death of his wife and young daughter in a car accident in 1972, to two early and unsuccessful presidential bids, to the death of his eldest son at just 46, his decades in Washington have been defined by tragedy but often followed by triumph.

Now, just four months after leaving office as a one-term president, and as intense scrutiny is placed on his mental and physical decline during those four years, the 82-year-old has been diagnosed with aggressive and advanced prostate cancer.

It is a disease that has never been far from his mind in the 10 years since his oldest son, Beau, died of brain cancer – leaving a deep emotional scar on the father that lingers to this day.

After that tragedy, finding a cure for cancer became a cause for the elder Biden.

In 2016, then-President Barack Obama tasked him with leading a "moonshot" government-wide research effort to that end - an effort that Biden continued during his own presidency.

Now it is cancer that presents possibly the greatest threat to Biden's health since he nearly died of a brain aneurism shortly after he abandoned his first presidential bid in 1988.

The news of the diagnosis lands as Democrats continue to grapple with the consequences of Biden's fateful decision to seek a second presidential term in the 2024 election – an attempt to extend the record he had already set for the oldest occupant of the Oval Office.

Biden ultimately dropped out of the race after intense pressure from Democrats following his halting, at times incomprehensible, performance in a general election debate with Donald Trump last June. But until that point, he had insisted that he was fit to continue in the White House for another four years.

This cancer diagnosis will underscore that the concerns about his age and the potential for health issues expressed by a majority of American voters in national polling were valid.

It coincides with the publication of several books detailing the efforts by those close to the president in the White House to accommodate, and conceal from the public, the toll the years were taking on his body and mind while he continued to serve as commander-in-chief.

While there is no reason to believe that Biden's prostate issues were at all apparent while he was in the White House, the fact that such an aggressive form of cancer could avoid detection until it had already spread, despite the wealth of medical support and evaluation available to Biden, will raise new questions and concerns.

It sets up a troubling hypothetical of how Biden's cancer might have been treated if he had successfully won a second term.

Hypotheticals notwithstanding, Biden's diagnosis may temper some of the sharper criticisms the book revelations would have otherwise prompted.

President Donald Trump, who had spent much of his recent trip to the Middle East disparaging his predecessor, released a statement extending his "warmest and best wishes" to the Biden family. That may be representative of the tenor of the public dialogue around Biden in the coming days.

Until several recent media interviews, including one with the BBC in which he defended his decision to stay in the 2024 race until a late stage, Biden had largely receded from public view since leaving power in January.

If the former president has the energy and endurance to do so, this latest medical revelation might give him a new platform, and a newly sympathetic public, to attempt to defend and burnish his presidential legacy.

Over the course of his public life, Joe Biden has defined himself by his persistence and endurance, only reaching the pinnacle of American power late in life.

His illness is another formidable challenge. But it presents one more opportunity for Biden to define himself – as a politician and as a man - by how he handles it.