Biden will not run for president in 2016

"While I will not be a candidate, I will not be silent," Biden told reporters in the White House Rose Garden with President Barack Obama and Biden's wife Jill at his side.

In deciding not to run, Biden, age 72, appeared to succumb to his own doubts about whether he and his family were ready for a grueling campaign while still mourning his son Beau, who died of brain cancer in May. His son had urged him to run.

Clinton's slipping poll numbers had cracked open a door to a late bid by the affable Biden, leading to calls from his supporters to seek the presidency.

But what was widely hailed as a command performance by Clinton in the Oct. 13 Democratic debate turned the tide back in her favor and quieted talk that she was vulnerable in her quest for her party's nomination for the November 2016 election.

Clinton's support among Democrats surged by 10 percentage points after the October debate, a recent Reuters/Ipsos poll showed. She had the backing of about 52 percent of poll participants, followed by Sanders at 27 percent. Biden's support, at 13 percent, was down 6 percentage points.

Biden had run for president twice before and was a U.S. senator from Delaware for more than three decades. Biden is popular with white, working-class voters, and he could still play a major role in the election if he chooses to endorse a Democratic candidate.

Also in the running for the Democratic nomination are former Maryland Governor Martin O'Malley and former Rhode Island Governor Lincoln Chafee.