While recent headlines have focused on the new “front runner” Elizabeth Warren, or the struggling Joe Biden, or the surging Pete Buttigieg, it seems that the resilient campaign of Bernie Sanders is slipping under the radar. Over the weekend, Sanders drew a massive crowd at a rally in New York City on Saturday with estimates of well over 20,000 in attendance, and more outside the gates trying to get in. The rally was more than just a typical Bernie rally since Rep. Alexandria Ocasio-Cortez took the stage to formally announce her endorsement of Bernie’s campaign.

The large rally, coupled with the October debate last week where Bernie fought to reinstate his commitment following his heart procedure earlier this month, seemed to bring the renewed vigor that Senator needs heading into the next three months:

Sanders’ campaign has a renewed vitality following a record-setting rally in New York over the weekend, a strong debate performance last week in Ohio, an infusion of campaign cash that translates to having more money on hand than any other Democratic presidential candidate, and endorsements from two of the most progressive women of color in Congress: Minnesota Rep. Ilhan Omar and New York Rep. Alexandria Ocasio-Cortez.

His campaign is optimistic and emboldened with a clear mission: prove the senator’s skeptics wrong and quash any lingering questions about his health and ability to serve after his heart attack.

“In the professional pundit class, in the elite media circles, there’s been a strong effort to discount Bernie Sanders: ‘The movement is over, he can’t succeed. He doesn’t have opportunities for him to grow, it’s gonna end for him,'” said Faiz Shakir, Sanders’ campaign manager, paraphrasing what he sees as a problematic narrative.

But Shakir contends that the last week proves the pundits wrong.

“Sanders has shown that he has the support and the stamina to stick around,” he said.

Sanders’ poll numbers have slid quite a bit since back in the late Spring when he sometimes topped Joe Biden depending on the poll or at least sat in a solid second-place in most instances. However, Bernie has always been capable of bringing in the fundraising dollars which means his campaign can be propelled deep into the primaries next year without fear that he would have to bow out for lack of money.

That fact alone, Bernie’s large war chest, makes him a continued threat for the nomination along with his strong backing of loyal supporters.

Then there’s the new interest in his campaign from Rep. Alexandria Ocasio-Cortez, a darling of the progressive left, who Bernie now says would serve in his administration if he takes the White House:

After freshman Rep. Alexandria Ocasio-Cortez officially endorsed Sen. Bernie Sanders for president at a Queens, N.Y. rally on Saturday, the Vermont progressive said he wants Ocasio-Cortez to work in his White House

Sanders was asked in a joint interview with CBS News if he would consider Ocasio-Cortez to be his running mate. The congresswoman answered for him as both laughed: “I think I’m too young for that.”

“There you go, she’s answered,” Sanders added.

But when Ocasio-Cortez was asked if she’d work in Sanders’ administration should he be elected president, he interjected with a forceful “Yes, you would.”

Running mate might be a little too much of a left-wing ticket for many voters to swallow. However, pledging to hire AOC in his administration serves just as well for some supporters of Bernie’s democratic-socialism who want to see more his policies implemented.

Why did AOC endorse Bernie over someone like Elizabeth Warren? The answer is simple: Bernie’s dedicated to the cause, she says:

Ocasio-Cortez, the youngest woman ever elected to Congress, said at the rally that the pressure that has been on her since she was elected to office made her “appreciate the enormous, consistent, and non-stop advocacy” of Sanders.

Sanders’ recent health scare was a “gut check,” Ocasio-Cortez told CBS. She informed Sanders of her decision to back his campaign while he was still recovering from a heart attack earlier this month.

“Neither me nor the senator cannot do this by ourselves,” Ocasio-Cortez said.

There was no chance of AOC endorsing Biden, he’s already been battling her surrogate groups for months now. Warren would have been the next logical option, perhaps the more “electable” option than Bernie, but that wouldn’t have met the objective of pulling the Democratic Party to the left.

Ocasio-Cortez says she had also spoken to other candidates, including Massachusetts Sen. Elizabeth Warren, ahead of her endorsement.

“I think she’s a fabulous candidate. Frankly, Sen. Sanders, Sen. Warren and myself are all on the same team in the party,” she said.

The same team, yes, but why withhold the endorsement from Warren? It’s possible that AOC feels Bernie is the only “true believer” in the field. Warren talks a good game, and has adopted many of Bernie’s policies, but will she push the “revolution” the way Bernie will? That’s an unknown right now as Warren is still navigating the primary. Ultimately, AOC said she’ll vote for whoever the nominee is, Biden included.

Bernie’s back on the campaign trail, with a slightly lighter schedule, and he shows no inkling to slow things down or lighten up on his anti-establishment, anti-wealth message:

“I am more than ready to assume the office of President of the United States. I am more than ready to take on the greed and corruption of the corporate elite and their apologists,” Sanders told a gathering of thousands of people holding aloft placards at the Queensbridge Park.

“To put it bluntly, I am back.”

As we reported on Monday, a new Iowa caucus poll shows Bernie back in fourth place now, with Mayor Pete Buttigieg jumping ahead of him in line. Biden and Warren remain tied. Fourth place isn’t a horrible position for Bernie, he’s still very much in contention and he has a strong ground game and enthusiastic supporters.

The next few months will be make-or-break for Bernie. Can he keep his supporters on board as Warren continues to chip away at his base? He’s certainly got the money on hand to put up a fight, it’s just a question of how best to deploy it and what kind of war he will choose to wage.