US vice president announces he won’t run in 2016 presidential election campaign, ending months of indecision.

United States Vice President Joe Biden has said will not run for president in 2016, ending months of indecision and removing one of Democratic frontrunner Hillary Clinton’s biggest potential obstacles to the party’s nomination.

Biden, 72, appeared in the White House Rose Garden with his wife Jill and President Barack Obama on Wednesday to say the window for mounting a successful campaign had closed.

Biden’s announcement ended a highly public “will he or won’t he?” political guessing game about his intentions that had shadowed Clinton’s campaign and frozen the support of some Democratic activists and donors.

“While I will not be a candidate, I will not be silent,” Biden said. “I intend to speak out clearly and forcefully to influence as much as I can where we stand as a party and where we need to go as a nation.”

US political analyst Jason Johnson told Al Jazeera he was not surprised by Biden’s decision.

“I don’t think he had a clear path to win the nomination…. If he thought he could win, if he was confident that he could beat [Clinton], then he would have entered the race,” Johnson said, adding that he did not believe the vice president would be able to affect the outcome of the contest.

“Joe Biden is not going to be a kingmaker in the process,” he said. “It’s now up to the candidates and the voters.”

Biden had been wrestling with doubts about whether he and his family were ready for a gruelling campaign while still mourning his son Beau, who died of brain cancer in May. His son had urged him to run.

Making good on his promise to speak out, Biden took a veiled jab at Clinton, chiding Democrats who referred to Republicans as their enemies and saying Democrats would be making a “tragic mistake” if they walked away from Obama’s record.

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Clinton had listed Republicans among her enemies during last week’s presidential debate and had broken with Obama by moving to the left on such issues as the Keystone XL pipeline and the Trans-Pacific Partnership.

Speculation about a Biden candidacy had grown as Clinton slumped in polls and questions grew about her honesty and trustworthiness amid the controversy over her use of a private email server while secretary of state.

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

A Clinton spokesman said she called Biden after he announced his decision. In a statement, she called him “a good man and a great vice president” and said she was confident he would continue to be on the political front lines.

Biden’s decision was a boost for Clinton, whose prime challenger now is US Senator Bernie Sanders of Vermont.

“She has no threats now,” Johnson told Al Jazeera. “There are no more threats.”