The Washington PostDemocracy Dies in Darkness

For the first time, a major poll shows Bernie Sanders leading Hillary Clinton

Democratic presidential candidates Hillary Clinton and Bernie Sanders fight for votes leading up to the Democratic primary in Nevada on Feb. 20. (Video: Reuters, Photo: MIKE NELSON/Reuters)

On Wednesday evening, NBC and the Wall Street Journal casually tossed a bombshell into the political world with a poll showing Ted Cruz with a slight lead over Donald Trump in Republican polling.

On Thursday, NBC and the Journal released the other half of that poll. Hillary Clinton continues to lead Bernie Sanders by 11 points nationally. Nothing shocking there, though it's closer than it used to be.* In fact, Hillary Clinton has never trailed in any national poll, so it's hard to see this as terribly surprising.

Or, anyway, Clinton had never trailed in a major poll when NBC released its survey. An hour later, Fox News dropped a bombshell of its own: Sanders has a 3-point lead, according to its new national survey.

A year ago, Clinton had a 52-point lead over Sanders, with 55 percent of support to his 3 percent. In Fox's last poll, conducted shortly before Iowa, she still led by 12. No longer.

At least according to this one poll. This poll is pretty remarkable in that every demographic has shifted in Sanders's favor, with him increasing his support and Clinton losing hers. In every single one. Where Clinton used to lead big, now the two are often tied. Where they were basically tied, Sanders has surged forward.

Certainly possible. But it's worth being cautious. In the words of Nate Silver:

We're not going to ignore this one, but we'll try not to obsess over it.

Fox also released a new survey from South Carolina today. In it, in a state where Hillary Clinton and Sanders have both been campaigning, the numbers are very different -- including among white voters.

South Carolina is not as liberal a state as Vermont, even among Democrats, but lots of other states aren't as liberal as Vermont, either.

As we noted about NBC's weird poll on Wednesday, this could perhaps be a signal of a big shift in the race. Or it could be a poll that's exploring the limits of the margin of error. As Silver points out, the average is the better indicator, and Clinton still leads in Real Clear Politics' average.

Though that Fox poll certainly did some damage.

* The NBC/Journal poll isn't the point of this article, but I did want to note this interesting question from it. Asked what concerned them most about Hillary Clinton, a fifth of Democrats said her ties to Wall Street. Two-thirds said nothing. Only 7 percent said it was the email server!

By contrast, only about half of Democrats weren't worried about Sanders's presented flaws, with about a quarter identifying his lack of foreign policy experience and another quarter identifying how "far out of the mainstream" his policies are.