Warren’s moves to start the new year amount to an effort to shift the national narrative and give her candidacy a boost after months of bombardment from rivals that came after she rose in national and early state polls. With just under four weeks until the first-in-the-nation Iowa caucuses — a state in which the campaign has invested a tremendous amount of time, money and staff — the once-surging senator is working quickly to try to regain her momentum.

In liberal New York, the event was something of a home game for Warren and a way to broadcast enthusiasm for her candidacy. The crowd — many people were decked out in liberty green Warren T-shirts and hoodless sweatshirts — began chanting “Warren! Warren! Warren!” well before she took the stage. Later, they broke into chants of “Two Cents! Two Cents!” in reference to Warren’s proposed wealth tax.

The Brooklyn event had parallels to an October rally in Queens that helped Bernie Sanders reignite his campaign. Shortly after suffering a heart attack and with his candidacy in peril, Sanders used the event, which drew more than 20,000 people, to brandish a new high-profile endorsement: Rep. Alexandria Ocasio-Cortez.

Castro does not inspire the fervent following of Ocasio-Cortez, and his presidential campaign never gained traction. But as one of the most prominent Latino officials in the country, the former HUD secretary is a high profile endorsement at a key moment. He's poised to play a big role for her in the coming weeks, with events scheduled in Iowa and likely more to come in Nevada and his home state of Texas. He could also be an important validator among Hispanic voters, a critical voting bloc in the Nevada caucuses.

There are also signs that Castro may join other Warren allies who've begun to attack her rivals more aggressively. Castro had already embraced that role on the campaign trail, especially as a critic of Pete Buttigieg.

Warren herself largely has avoided attacking her rivals over the course of the campaign, in hopes of being a unifying candidate in the primary. After an extended row with Buttigieg last month over allowing news media into his private fundraisers and releasing the names of his bundlers — steps he ultimately took — Warren has seemed intent on returning to a positive, above-the-fray posture.

Tuesday night, an audience member jeered “Mayor Pete” as Warren dinged Democrats who sound “oh so smart backing off from big ideas.” Warren paused and then joked: “I didn’t hear that.”

But two top Castro aides did not show similar restraint Monday and Tuesday as they bashed Joe Biden for saying he would require undocumented immigrants to learn English in order to obtain citizenship. “It’s time we dispel the notion of good and bad immigrants based on their ability to speak English,” said aide Sawyer Hackett on Twitter.

“My dad became a naturalized citizen ~25 years ago, and to this day still doesn’t speak English,” Castro aide Natalie Montelongo tweeted about Biden. “As a 2nd grader I stayed up countless nights helping him memorize questions/answers in a language he didn’t know. It was hard to see him struggle. It shouldn’t have to be that way.”

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(“The verbal portion of the naturalization exam is administered in English (except for in very select cases) and our plan offers English language education support,” a Biden campaign official said of the candidate’s remarks.)

The outside group Progressive Change Campaign Committee, which has endorsed Warren, has also gone after Biden and Buttigieg lately.

The Warren campaign has been trying to go on the offensive as well, albeit more cautiously. Tuesday morning, it released a plan to roll back sections of the 2005 bankruptcy bill that Biden championed and Warren fought against at the time. “I lost that fight in 2005, and working families paid the price,” Warren wrote in a Medium post in an implicit jab at Biden. She did not mention the plan or Biden at the Brooklyn rally.

The PCCC said what Warren wouldn’t. “When thinking about electability, it would be complete malpractice to nominate someone who conspired in backrooms for years with credit card lobbyists and voted for every corporate bankruptcy bill, Wall Street deregulation, and trade deal that voters hate,” said co-founder Adam Green. “Biden would ironically cede the outsider mantle to a corrupt incumbent president.”

Castro, greeted by a lit theater marquee at the event featuring his name with Warren's, leapt right into his role as a surrogate. The Texan was vetted to be Hillary Clinton's running mate in 2016 and has drawn buzz about the same possibility during this election cycle.

“The polls say this and that,” Castro told reporters before his inaugural appearance with Warren. “I saw very clearly — what counts on the ground in Iowa is the organization that you have, and there is no organization stronger, more enthusiastic, more committed than the organization that Senator Warren has.”

Or, as he later told the crowd: “Elizabeth Warren has the best damn organization in the early states.”

