Joe Biden: The most popular (undeclared) candidate?

In head-to-head match-ups against Republican rivals, Biden trumps Hillary Clinton, beating each rival by a larger margin.

Joe Biden may not have made a decision for 2016 yet, but he's already the most popular (undeclared) presidential candidate in the race. 

Consider this: Mr. Biden enjoys an 80 percent favorability rating among Democratic voters, higher than any other candidate in the field.

One quarter of Americans who are registered Democrats or lean that way say Biden is now their top choice for president, according to a recent Bloomberg poll. That puts him on the heels of Hillary Clinton, the top choice of 33 percent, and within the poll's margin of error of Bernie Sanders.

In head-to-head match-ups against Republicans, Biden beats each rival by a larger margin than Mrs. Clinton. 

What's more, he's already eligible for the first Democratic presidential debate, scheduled for Oct. 13 in Las Vegas. All he must do to participate is declare his candidacy before the debate starts. 

All this for a man who has not yet declared anything. 

Even as Clinton, the presumed Democratic frontrunner, continues to stumble in the polls thanks to an ill-timed email controversy, the vice president is openly weighing another presidential run. It would be his third shot at the White House since 1988 and a late entry in a race already full of surprises. But Biden and his family are grieving over the death of his son Beau Biden, who died in May, and the vice president has indicated that he will not run unless it is good for the entire family. 

That hasn't stopped the rest of the political world from counting Joe in. 

His favorability ratings have risen as Clinton's have fallen, points out Bloomberg. 

Some 40 percent of Americans have a positive impression of the vice president, while 28 percent have a negative impression, giving him a net rating of +12, compared with +10 for Vermont's Senator Sanders and -8 for Clinton, according to a new NBC News/Wall Street Journal poll.

If the 2016 election were held today, Biden would have a better shot at beating a Republican rival than would Clinton, according to the NBC/WSJ poll. 

Voters say they’d back Clinton over Donald Trump by 10 points (49 percent to 39), but the former secretary of State would be statistically tied with Carly Fiorina (45 percent for Ms. Fiorina, compared to 44 percent for Clinton), Ben Carson (46 percent for Dr. Carson, compared to 45 percent for Clinton) and former Florida Gov. Jeb Bush (44 percent for Mr. Bush, compared to 45 percent for Clinton).

But Biden would do better, the poll finds, besting Bush by eight points (48-40), Fiorina by six points (47-41), Carson by eight points (49-41), and Trump by 19 points (56-35). Sanders would also beat Trump handily (52-36), but the poll did not match Sanders against the other Republican candidates.

A Biden candidacy could be "a real nightmare for the Clinton campaign," said Bill McInturff, a Republican pollster who conducted the survey with Democrat Fred Yang, to The Wall Street Journal. Biden "could pick off votes and put states in play."

In fact, the poll results suggest Biden would siphon support, including minority voters, almost entirely from Clinton, rather than from Sanders. It's enough to scare the Clinton camp – and further encourage Biden supporters. 

What does it say about the Democratic field that a man who hasn't declared anything is already its most popular candidate? 

Perhaps that the base is antsy about backing a presumed frontrunner who is beleaguered by an email controversy that has become a serious liability. And that the next best alternative is a self-described socialist who's still not universally known and who may prove too liberal for many. Or that the remaining candidates poll so low and remain so unfamiliar they barely register in the headlines, the polls, or most voters' consciousness. 

Biden, by contrast, is seen as a breath of fresh air – he is relatively moderate and universally recognized where Sanders is not; open, trusted, and likable where Clinton is not. 

And Biden is on a roll. Viewers loved his much-talked-about interview with Stephen Colbert on CBS's "Late Night," in which the vice president shared his love for his son Beau. It was a moving display of the authenticity and openness for which Biden is known.  

Will it last? 

Political wisdom has it that a candidate is most popular just before declaring. At this point, excitement runs high and coverage is centered around the "will he or won't he" question. No one has examined his record, highlighted his gaffes, attacked his past positions, or challenged his platform. 

In Biden's case, he's got the additional goodwill that came from the outpouring of sympathy after the tragic death of his son, and the additional name recognition that comes from being a well-known and well-liked vice president. 

And if he does declare?

As Republican pollster Bill McInturff told NBC News, "History has shown that the public has a much harsher filter when people become candidates."