Joe Biden is not running for the White House: 'The window has closed'

The 72-year-old has been pondering a possilble run since the death of his son this summer

Activists fear a vote for a third party could hurt Joe Biden (Reuters)

One of the most hotly watched political guessing games of recent times is over - Joe Biden is not running for the White House. "The window has closed," he said in the Rose Garden on Wednesday.

Watched by President Barack Obama and his wife Jill, he added: "While I will not be a candidate, I will not be silent."

The worlds of politics and punditry have been little shot of obsessed since it emerged this sumer that the vice president had been persuaded to actively consider another run - he ran previously in 1988 and 2008 - by the dying words of his son Beau.

As he grieved for his son, who died at the age of 46 from brain cancer, reports had said Mr Biden believed he had an opportunity in a field that contained Hillary Clinton, Martin O'Malley, Bernie Sanders, Jim Webb and Lincoln Chafee. As Ms Clinton watched her poll numbers slip, some believed there was an opportunity for the veteran Delaware politician to find a gap, and campaign as a unifying figure who could unite the country.

But many were persuaded to rethink that after the performance in last week's debate by Ms Clinton, the assumed Democratic front-runner. She was confident and chisselled, but also displayed a more human touch than many had witnessed for some time.

Indeed, in the aftermath of the debate, Ms Clinton's support among Democrats surged by 10 per centage points, a recent Reuters/Ipsos poll showed. She had the backing of about 52 per cent of poll participants, followed by Mr Sanders at 27 per cent. Mr Biden's support, at 13 per cent, was down 6 points.