Joe Biden knew he was capable of beating Hillary Clinton in the presidential race - but decided not to run fearing a 'stop at nothing' campaign by her backers, the former vice president has revealed in his new memoir.

In Promise Me, Dad: A Year of Hope, Hardship, and Purpose, set to be released November 14, Biden reveals how he wrestled with the idea of running for office before and after his son Beau's death, and even admits he did not want to be Obama's vice president in 2008.

The book documents Biden's life as President Obama's tenure drew to a close and the media's focus had shifted to the prospects of the presidency.

It is certain to fuel the bitter infighting in the Democrats which has lasted since they were shocked by Clinton's defeat a year ago Wednesday.

Biden offers little direct personal criticism of Clinton but his message is unmistakable.

'My numbers on trustworthiness, honesty, and empathy were as high as they had ever been. And I was strongest where the most formidable candidate, Hillary Clinton, was weakest: the key swing states like Pennsylvania, Ohio, and Florida,' he writes.

Revelations: Joe Biden spells out his uncomfortable decision not to run against Hillary Clinton and speaks of how he feared he could not control his anger if the death of his son Beau was used against him

Mourned: Beau Biden's death in May 2015 was followed by a public funeral and then, for his father, months of agonizing over whether to run. Beau had told him she should

My son: The loss of Beau Biden was the deciding factor in Joe Biden's decision not to run - but Obama's vice-president reveals how he was afraid he could not control his rage if it was used against him.

Clinton lost all of them in the election, part of the reason why she was defeated by Donald Trump.

And he speaks candidly of how he feared 'opposition research which would 'stop at nothing' in the days before he announced he would not run.

WHAT BIDEN DOESN'T MENTION IN HIS BOOK... A SAD STORY OF SEX, DRUGS AND GRIEF Joe Biden's book makes no mention of the drama that plagued his fractured family after Beau's death Court documents revealed Hunter Biden's marriage to Kathleen disintegrated shortly after Beau died - at exactly the time a newly-bereaved vice-president was trying to decide whether he should run. She later revealed that she kicked him out on July 5, 2015 because of 'his conduct the night before'. His brother had been dead a little more than a month. In August 2015, when Joe Biden was rising to the top of the polls, Robert (Hunter) Biden's name was found among the hacked records of users on the extramarital affair site Ashley Madison. Hunter denied having an account on the site. But DailyMail.com established that the credit card used for the Ashley Madison account was registered to one of Biden's Washington D.C. addresses. He then claimed the card had been stolen. DailyMail.com was unable to obtain a matching police report. Two months after the Ashley Madison link emerged the couple formally separated, which would have also been right around the same time that Joe Biden announced he would not seek office. The news of their split was never made public until this year, when it was revealed Hunter Biden was dating his brother's grieving widow. Kathleen Biden's allegations that he was living a seedy double life were detailed in court documents lodged in February 2017. The couple had 'overwhelming' debt, she told the court, had bounced checks, owed $313,90 in taxes, and he had cut child and spousal support fromn $17,000 to $7,500 a month the previous October. Eventually the case was settled without public comment from Kathleen Biden. Advertisement

Clinton was the only opposition to him - and what he does not say in the book is what 'stop at nothing' would mean.

But at the time his bereaved family was being torn apart by his surviving son Hunter's bitter split from his wife amid accusations of blowing a fortune on drugs and sex with prostitutes.

Hunter then started a new relationship, with his brother Beau's widow.

Biden is to start promoting the book with an appearance on the NBC's Today show on Monday and an extended book tour which will see him appear on stage with big names including Stephen Colbert, Aaron Sorkin, the writer of the West Wing, and Maria Shriver, Arnold Schwarzenegger's ex-wife and a member of the Kennedy clan.

The tour is likely to be seen as part of a move towards another run for the White House by Biden, whose book does not rule one out or suggest that his public life is over.

It even includes a detailed list of policies which he would have run on.

And it makes clear how Biden was convinced he would have beaten Clinton, who he called a 'vulnerable' candidate.

By early August of 2015, three months after Beau succumbed to brain cancer, Biden's ratings were higher than any other candidate in the race, despite the fact that he had not made an official decision to run.

The campaigns being run at the time, he writes, were 'dreary, small and personal' - another hit at Clinton's effort for the White House.

Biden's family were also confident he could take the presidency, he writes, saying they believed 'I was best equipped to finish the job Barack and I had started.'

In fact, if there were any doubts the VP would falter, they came from President Obama himself.

'In January 2015 the president was convinced I could not beat Hillary, and he worried that a long primary fight would split the party and leave the Democratic nominee vulnerable in the general election,' Biden writes.

Around that time, Obama had become 'preoccupied' with the question of whether Biden would run and had been 'subtly weighing in against' it.

'Barack and I knew, coverage in the West Wing would shift from his agenda to my chances. I also believe he had concluded that Hillary Clinton was almost certain to be the nominee,' he says.

By then, Clinton was already preparing to launch her campaign and became vigilant of Biden's moves.

He reveals a meeting the two had - and details how she offered an implied threat that she could not control her own supporters.

During a meeting in February 2015 at his Naval Observatory residence, she 'had an entirely new agenda' Biden writes.

'She started off telling me what a good vice president I had been, how much I had done for the country in my career...Then she pretty much asked me straight up if I was going to jump in.'

Biden told her he was not in a position to make the decision at the moment. His son's health was deteriorating but he did not tell her the full extent of the cancer the former soldier was battling.

Family: Joe Biden kissed his granddaughter Natalie before the requiem mass for her father Beau. Her mother Hallie, Beau's widow, is now in a relationship with Hunter (left), Beau's surviving brother. The two are now in a relationship after he split in an ugly public tussle from his wife Kathleen

Opposition research: Joe Biden does not mention the family scandal in the background of his decision not to run, with Kathleen Biden divorcing Hunter, claiming he had blown their savings on drugs and prostitutes. Hunter then began a relationship with his brother's widow. None of this was public as the 'opposition research' began

Biden also admits how he initially did not want to serve as Obama's VP in 2008, saying the position had a 'long and storied career - as a punchline.' Obama also believed Biden could not win against Hillary Clinton

'But if I ran, I told her, I would not run a negative campaign. She said the same,' he writes, but then she said: 'Although some of our supporters can get out of hand sometimes, it would not be me.'

That summer, when Biden started to receive calls from people encouraging him to run, he reveals there were also 'a few different kinds of messages being sent my way through the press.

If this thing about Beau came up somewhere in my hearing, I was afraid I would not be able to control my rage. And I would say or do something I would regret Joe Biden on the days before he decided not to run when 'opposition research' began on him

''I just want the vice president to do what's right for him and his family,' Hillary said at a campaign stop in Iowa.'

She went on to sing his praises saying she had a great deal of admiration and affection for him, but by then, Biden says, 'the opposition research had already started on me.'

He does not say who it was from but he writes elsewhere of the 'Clinton machine' which Obama barely beat.

Biden reveals how he became the target of a political hit job in the media after a there was a story published about the community policing crime bill that he had created under Bill Clinton's term that the president had once heralded as a great step forward.

'He was now calling it a big mistake. That was followed by a story alleging I was cozy with the banking and credit card industry when I was a senator,' Biden writes.

'And Clinton backers sent the signal that they would not stop at voting records and policies if I did get in the race.'

But Biden said he focused on the 'calls of support,' which included one from George Clooney who was keen on joining his campaign.

'An executive in the entertainment industry had insisted that I had more support in the Hollywood community than Hillary. He said I could raise money without a problem. George Clooney got in touch with Steve Ricchetti soon after that,' Biden writes.

Clooney told his chief of staff: 'I love Joe Biden, and if he decided to do this I will step up with any and all assistance I can provide. I think I've proved I'm pretty good fund-raiser, so that's all anyone asks me to do. But I am invested in this. I am willing to take a campaign role if you want me.'

Beau Biden's death had been at the center of the VP's debate of whether or not he'd run for office. Beau succumbed to brain cancer in May 2015 (above Joe is pictured with wife Jill and his family at his son's funeral mass)

Clooney went on to become a major Clinton supporter, but his intervention suggests that she was his second choice.

Biden continued to gain momentum in the polls which ultimately scared Clinton's team.

'The head of AFL-CIO (American Federation of Labor and Congress of Industrial Organizations) was saying nice things about me, which was causing great consternation at Hillary's headquarters,' he writes.

Her team began placing calls to his aides which he described as 'fishing expeditions,' in which they would ask: 'So what are you guys up to? This isn't for real, is it?'

Although Biden had been making headway for months, he still hadn't made an official decision about entering the race.

In the immediate aftermath of Beau's death, just thinking about running for president was 'beyond me,' he says.

Beau had been his biggest supporter, having encouraged him to run from the get-go. But throughout the year, Biden struggled with his own grief and often doubted he had the emotional strength to campaign.

'If Beau had never gotten sick, we would already be running. This is something we would've done together, with enthusiasm. The thought of doing it without him was painful. But as the days passed, the idea of not running started to feel like letting him down, like letting everybody down,' he writes.

As the election year drew near, and there had been no official word of Biden's decision to enter the race, Beau's death inevitably became a political pawn.

In October 2015, Politico published a story titled: 'EXCLUSIVE: Biden himself leaked word of his son's dying wish,' which stated: 'Joe Biden has been making his 2016 deliberations all about his late son since August.'

'I should have seen this coming, I guess,' Biden writes. 'The Politico story exceeded even my worst expectations of what the opposition was going to be like. The idea that I would use my son's death to political advantage was sickening.'

It wasn't until later that month, that Biden had made up his mind that he would not run in the 2016 presidential election. The decision was influenced by his counselor Mike Donilon during a campaign meeting in later October.

Promise Me, Dad: A Year of Hope, Hardship, and Purpose, will hit bookshelves on November 14

''I don't think you should do this,' he said. It was the first time he had spoken against my running in the two years we had been talking about it.'

'I understood Mike wasn't speaking as a political strategist, because I knew how profoundly he believed in my candidacy and that he still believed, like I did, that we could win. He was speaking as a friend.'

That night, Biden made his decision and finally announced the next morning in the Rose Garden that he would not be running.

In his book, he also makes the shocking revelation that he struggled with the idea of serving as vice president in 2008, almost as much as he did with debating whether he'd run for president.

'[Obama] asked my permission to vet me, and I said no. 'I'll help you anyway I can,' I told him, 'but I don't want to be vice president.' I obviously didn't say this lightly,' Biden said.

'I had been in Washington long enough to watch eight different vice presidents, and I knew the history. The office itself has a long and storied career - as a punchline.'

Biden's reluctance also stemmed from the fact that if he took the job, he'd be doing something that he had not done for 40 years: working for somebody else.

After discussing the opportunity with his family, Biden came around the idea, and told Obama he needed to be 'the last guy in the room on every major decision,' to which Obama agreed.

'We got on the phone and told the entire family. And I didn't doubt for one moment that we had made the right decision.'

Promise Me, Dad: A Year of Hope, Hardship, and Purpose is available for pre-order on Amazon.com