Why Joe Biden's big decision could hinge on Hillary Clinton

Vice-President Joe Biden is still keeping Washington waiting on his big decision whetherto runin the 2016 Democratic presidential race, and the front-runner in it, Hillary Clinton, could be a reason why it's taking him so long.

There are likelymany factorsgoing into Biden's decision, including his grieving family(his son Beau died this summer of brain cancer) and the challenges associated with mounting a campaign this late in terms of fundraising, staffing and other infrastructure, not to mention polling numbers. Although he hasn't declared a candidacy, he's regularly included in polls and regularly falls behind Clinton.

But the Clinton calculation is also thought to be playing a role in Biden's decision. Her performance in the campaign, for better or for worse, may ultimately determine if the 72-year-old vice-president tries to keep a job at the White House.

"If Clinton hadn't had a bad summer, I doubt Biden would actually be in the mix here. I think Clinton has shown a little bit of weakness and that's opened the door up for Biden," saidKyle Kondik, of the University of Virginia's Center for Politics.

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Biden has been mulling over the idea for months and will reportedly makea decisionany day now. On Monday night he met with advisers;he'smadecalls to Democratic operatives, setup interviews for potential campaign positions, and last week a close confidantsent an email to former Biden staffers asking them to be prepared to help if he does decide to go for it.

The pressure on Biden to run rose over the summer, particularly as Clinton started to slip in the polls and Vermont Senator Bernie Sanders, her top rival, gathered momentum. Some Democrats worry Clinton won't be able to win against the Republican nominee, and they want a strong alternative candidate like Biden.

Clinton to testify again on Benghazi

Clinton's use of a personal email server while secretary of state continues to loom over her and to affect her trustworthiness rating with voters. Republicans are also still driving a special committee investigation into what happened in Libya in 2012 when she was in charge of the state department.

Clinton will appear at that committee on Thursday to face tough questions about the attack on the U.S. Consulate in Benghazi that killed ambassador Chris Stevens and three other Americans.

It will be a closely watched appearance the last time Clinton testified she got testy and defensive and Kondik suspects Biden willtunein to see how it plays out.

"Depending on how that's covered and how people react to it, one might think that that would have some bearing on whether Biden decides to get in or not," he said.

If it goes badly for Clinton, it could kill the boost she got last week from the first Democratic debate and provide Republicans with more ammunition to attack her. Clinton, Sandersand the three other men who were vying for the nomination (Martin O'Malley, Lincoln Chafee and Jim Webb, who dropped out of the race Tuesday) faced off in Las Vegas, and by most accounts Clinton had a solid performance.

She came across as confident and well-prepared, strongly defended her record and reasserted her front-runner status. Even Sanders, who is trying to beat her, said Americans are sick of hearing about her "damn emails."

Some pundits and strategists, such as Hilary Rosen, were watching Clinton that night with Biden in mind.

Is there a path for Biden?

"I've been looking at this tonight wondering where the path is for Vice-President Biden, and I think that path is narrowing," Rosen said in an interview during the debate on Oct. 13. "It's just not clear that there's a place for him to fit in here. These are two strong candidates," she said, referring to Clinton and Sanders.

There is a theory circulating that Biden would feel compelled to run only if Clinton's campaign seriously flounders. The popular vice-president, who is well respected in his party, would act as a sort of saviour to try to ensure that the White House stays in his party's hands.

"I think his one path to the nomination is a Clinton implosion," said Kondik. "And whether that happens while Biden is actually a formal candidate or whether she collapses and then he rides to the rescue at the convention, that to me is the path. I think his success is contingent on her failure in some way."

Her performance at the first debate seemed to reassure some Democrats that she will be just fine in the general election and that she closed the window on Biden entering the race.

But if he does challengeClinton for the nomination, Biden will need to offer Democrats a rationale for doing so. Why him and not her? If she's doing well, the answer to that question is less obvious.

Democratic strategist Donna Brazile wrote on her blog that if Biden runs it won't be because he thinks Clinton is a flawed nominee, "but because he believes that he simply has more to offer."

"I believe if Biden chooses to run it will be because he's reassessed what he brings to the presidency that no one else does, and feels it's compelling enough to fuel and fight a gruelling campaign," she wrote.

Biden should be compelled one way or the other soon, because deadlines to get on the ballot in certain states for their primary elections are just a few weeks away in early November. If he wants to be more than the backup candidate for Clinton and mount a real campaign, he has to act fast to get his name next to hers on those ballots.