Analysis - US President Joe Biden, who channelled perseverance and grit into a 50-year run in American politics, finally met a foe he could not beat.
His opponent in the November presidential election was technically former president Donald Trump, but it was also a much, much harder one to beat - age and perception.
The disastrous June debate performance - the worst I have watched in 40 years of viewing these frustrating, fascinating American events - laid bare the harsh reality of age on America's oldest president, and in US politics, image is everything.
At 81-years-old - 82 in November - Biden finally recognised today he could not win this one.
My own father died in May at 83-years-old, just a little bit older than Biden. Up into his 80s, he was a tremendously strong, vital and charismatic man, until one day, he was not.
Dad did many great things in his life but as he battled pancreatic cancer, he would often repeat one of our family's favourite sayings: "It is what it is."
The events of the past month have taken on the feeling of a slow moving car crash, and Biden's decision has shaken up the 2024 race in a way that may have many Americans exhaling with relief, while others will fume with frustration.
The cascade of senators and congressional leaders from Biden's own party stepping away from his campaign was something unprecedented in presidential races of the past 40 years. A media avalanche of calls for Biden to give up - some fair, some cruel - never ceased, despite attempts to beat it back. We saw plenty of articles with doctors doing long-distance diagnoses of Biden's possible medical conditions.
Age is not a scandal. It is not something you can beat back with good comms, or perky memes. (The "Dark Brandon" attempts to make Biden some sunglasses-wearing superhero were cute at first, but rapidly started to feel a bit cringe.)
Every US president has aged dramatically in office - but for Biden, already past an age most people have retired, the optics were hard to overcome.
Contrary to armchair doctors all over the internet, I have never thought that Biden has dementia. I have family members with dementia, and frankly, the overwhelming tsunami of hot takes online that apparently, everyone over the age of 65 has dementia, were pretty insulting.
But Biden has slowed down, as all of us do in the end.
The biggest obstacle to his run for a second term was the realisation that Americans were not just being asked to vote for the Joe Biden of 2024, they were being asked to vote for the Joe Biden of late 2028 who would be 86-years-old and all the Joe Bidens in between.
While Trump, 78, manages to still summon up a fierce energy at his rallies, now that he will be the oldest candidate in the race, he may face far more scrutiny than before about how Trump 2024 and Trump 2016 are different. Even Trump has to face age in the end.
Only a handful of US presidents have made the decision Biden did today, and none of them so late, or quite so old as Biden is.
The obvious comparison to be made now is Biden - reluctantly, but civilly - giving up the ongoing power of the presidency, and Trump, on 6 January 2021, doing everything he could to hold on to it.
Nobody quite knows what will happen this November, but the playing field has changed forever today. For Biden, it has to be a sombre, frustrating day, but in the end, age cannot be explained away easily.
As my late great dad would have said: "It is what it is."