The evidence here is circumstantial, as it always is with polling, and it’s further complicated by the fact that his post-heart-attack return to the campaign trail is all but impossible to disentangle from AOC’s endorsement. Has he risen in the polls because she backed him, or has he risen in the polls because fans who had been wavering after his health scare felt a burst of goodwill upon watching him vow to fight on?

She endorsed him on October 19th at a “Bernie’s Back” rally in NYC. How can we isolate either variable from the other?

Whatever the truth, something does seem to have changed in the RCP national average shortly after the rally. Note the dates in the graph below:

In mid-October he was at 18 percent in Politico’s poll. He’s at 20 now. YouGov had him at 13 percent then and at 16 percent now. He went from 22 percent in an Emerson poll taken in late September to 25 percent more recently. A Quinnipiac survey conducted a few days before the AOC/Bernie’s Back event had him down to 11 percent. But a follow-up poll taken between October 17-21, which included the day of the rally and two days afterward, took him up to 15 percent. Hmmm.

Maybe Bernie really is back.

Today CNN dropped the best poll for him that he’s had in ages. This was taken in New Hampshire, not nationally, but it’s sure to cheer his campaign: He’s now the leader in the field, passing Biden and his rival Warren.

Vermont Sen. Bernie Sanders (21%) and Massachusetts Sen. Elizabeth Warren (18%) are in a close race among likely voters in New Hampshire’s first-in-the-nation Democratic presidential primary, according to a new CNN poll conducted by the University of New Hampshire…

Sanders has widened his edge as the most progressive candidate in the field: 47% see him that way, up from 40% who said the same in July. Warren has slipped on this measure, dipping from 23% to 18%. Sanders has also pulled ahead when likely voters are asked to name the most likeable candidate in the field, 27% name him, 20% Biden, 14% Buttigieg and 10% Warren.

Sanders tops the field as best able to handle health care (33% Sanders, 17% Warren, 15% Biden) and the climate crisis (30% Sanders and 15% Warren) — the two issues which top New Hampshire Democratic voters’ priority list — while lagging a bit behind Warren (21%) and Biden (20%) on the economy (15% say Sanders would be best on that).

It looks like he’s improved a bit in Iowa too. The one poll taken there since October 19 places him at 18 percent, one of his best showings since August. Then again, the same poll gave Warren her best number in Iowa of the entire campaign thus far — 28 percent, good for an eight-point lead. And it wasn’t Bernie or Joe Biden behind her in second place. It was Pete Buttigieg, who cracked 20 percent in Iowa for the first time.

All of which is to say that we shouldn’t overstate the AOC/Bernie’s Back effect even as we’re paying attention to his rebound. The effect isn’t so large that he’s passed Warren as the progressive choice, today’s CNN poll aside. And it’s not so large as to place him even in the top two in Iowa. In fact, Bernie is fourth in the RCP average there at the moment. He may have a new problem too in the form of Andrew Yang, whose campaign chugs on and continues to attract lefties who are looking to shake up the system in a radical way via Yang’s UBI idea. They might be Bernie voters if not for him. So not only does Sanders have to figure out a way to pass Warren, not only does he have to convince primary voters that a 78-year-old with heart problems is worth gambling on as nominee, he also has to hold off a much younger guy with even more of an “outsider” pitch than Sanders himself.

As for Grandpa Joe, hoo boy:

Joe Biden risks a humiliating third- or fourth-place finish in Iowa early next year, according to nearly a dozen senior Democrats in the state who attribute the prospect to what they see as a poorly organized operation that has failed to engage with voters and party leaders.

With fewer than 100 days until the Feb. 3 caucuses, Biden is failing to spend the time with small groups of voters and party officials that Iowans expect and his campaign’s outreach has been largely ineffective, according to 11 senior Democrats in the state. That could send Biden to a crippling loss behind Elizabeth Warren and Pete Buttigieg, who have highly organized campaigns in Iowa, said the Democrats, most of whom requested anonymity to speak candidly about the campaign…

“I think it’s fair to say if action isn’t taken soon, you’re going to find that a person who was 7 or 14 points behind Biden will be breathing down his neck or actually ahead of him,” said Kurt Meyer, chairman of the Mitchell County Democratic Party. “There’s still time because the caucuses are not on Oct. 27, but action needs to be taken.”

He’s still ahead in national polling but no one believes that the national polling will hold if Biden gets beat in Iowa and New Hampshire, especially if he’s beaten badly. “Electability” is propping him up. Shatter that pillar by handing him a couple of big losses early and who knows how quickly the whole campaign might collapse. He’s still technically in second place in Iowa in the RCP average but the last two polls of the state had him under 20 percent and, as noted already, he trailed both Warren and Buttigieg in the latest one. Buttigieg has obvious polling momentum; Bernie seems to be making a comeback; Warren leads the entire field; but there’s no similar cause for optimism for Biden. He also trails Warren in New Hampshire and has Sanders right at his heels there for second place. Imagine Joe finishing fourth in IA and then third in NH and limping into South Carolina to try to convince black voters that they should stick with him. That’s a realistic scenario, and it’s getting more realistic by the day.