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Scratch Joe Biden off Brooklyn's list of worries.

The announcement Wednesday afternoon that Biden would not enter the presidential race removed another hurdle for Hillary Clinton, whose string of good fortune was kicked off by a strong Oct. 13 debate performance that boosted her standing in national polls. Biden's decision takes some of the pressure off for the immediate future and makes Clinton's delegate hunt easier as she moves to shore up her party’s nomination.

Biden’s Rose Garden announcement, with President Barack Obama standing by his side, was greeted with relief among Clinton staffers and allies, who maintained that the former secretary of state would beat Biden but did not relish what they predicted would become a difficult slog through the primary — not to mention a personally challenging one for some of Clinton’s most senior aides, like policy adviser Jake Sullivan, and top donors who maintain strong personal ties to the vice president.

“It makes things a lot less complicated,” conceded Clinton donor Jay Jacobs.

On Wednesday, Clinton allies credited Biden’s ultimate decision not to run with the Clinton campaign’s success in boxing him out behind the scenes, and publicly refusing until the very end to engage with him. “The idea was to give Biden the room to make a decision while letting him know it would be hard to win,” explained a close Clinton ally.

Since Biden began floating the possibility of a run last August, some Clinton supporters worried privately that the campaign had been too meek in its response, even as he ramped up his thinly veiled criticisms of Clinton.

Clinton herself maintained a respectful distance from Biden’s decision — even when the calculus of his run was predicated on the idea of her weaknesses as a candidate — saying only that he “should have the space and opportunity to decide what he wants to do.” Her campaign remained silent even as the criticism grew more personal: A spokesman declined to comment Tuesday when Biden contradicted Clinton’s account of supporting from the beginning the 2011 raid that killed Osama bin Laden. And the campaign also refrained from comment after Biden said it was “naive” to call Republicans enemies, as Clinton did during last week’s Democratic debate.

The closest the campaign has come to publicly pressuring Biden came last week, when campaign Chairman John Podesta said “it is time for him to make a decision.” And Clinton even backed away from that milquetoast push in an interview with Jake Tapper on Sunday. “Well, that’s up to Vice President Biden,” she said when asked if she agreed with Podesta that the time for a decision has come.

Some allies have encouraged the campaign to do more to fight back — even floating the idea of engaging outside groups like EMILY's List to mount a bigger pushback against Biden, or rallying more elected officials to make the case for Clinton. Another source said there were some early discussions about whether it made sense for campaign surrogates to explain why Biden would not win, but even that tactic was shelved. A Clinton spokesman did not respond to a request for comment.

The directive to do nothing publicly to challenge Biden, multiple sources said, came directly from the top — Hillary Clinton herself was described as “aggressive” and “demanding” that donors and outside surrogates refrain from launching attacks against Biden or even commenting publicly about his support or his chances.

“Speaking to people in the campaign, they made it very clear that in no way did Hillary want anybody saying anything negative about the vice president,” Jacobs said. “She was very clear about that.”

The campaign was so sensitive about the appearance of going after Biden that even talking points for surrogates on how to discuss the vice president, usually delivered by email, were delivered only through private phone calls. “Everything I’ve been told by the campaign is, ‘Don’t go after him, we’re not going after him,’” said another close ally of the campaign.

Part of that stance was out of respect, sources close to the campaign said, and part was an effort not to give Biden any reason to feel he should get in the race.

Clinton was eager to distance herself from a report that her defender David Brock was conducting opposition research into Biden’s past through his PAC, Correct The Record, which coordinates with her campaign. “I have no knowledge of it,” she told PBS’ Judy Woodruff. “I don't know anything about it.” But Brock did not deny collecting dirt that could be used to challenge Biden if he got in the race.

Yet Clinton made quiet moves that sent Biden a clear message: Don’t run. 

Last August, just after the first Biden trial balloon was floated in a column by Maureen Dowd in The New York Times, Clinton cut short her Hamptons vacation to make an appearance in Ankeny, Iowa, with Agriculture Secretary Tom Vilsack by her side. Her words there were that Biden "has to do what he has to do, I’m going to continue with my campaign.” But her actions sent a loud and clear message to Biden: I’m going to be here fighting on the ground, even if it means interrupting my vacation, campaigning with the support of members of the Obama administration, not giving you an inch.

Instead of launching public attacks, the Clinton campaign sought to shore up support from heavy hitting unions like the National Education Association. It rolled out endorsements from Obama administration officials Vilsack and Housing and Urban Development Secretary Julián Castro. It quickly pushed out a list of 50 African-American mayors supporting Clinton’s bid (even though at least three people on the list later said they had not yet actually committed to supporting her). Last August, as Biden called into the Democratic National Committee meeting in Minneapolis, Clinton campaign officials told Bloomberg News that Clinton already had 130 superdelegates publicly supporting her and that privately she had shored up 20 percent of the superdelegates necessary to win.

On the debate stage, Clinton embraced Obama, a move that made it more difficult for Biden to pitch himself as the Obama legacy candidate. And she moved leftward on a number of issues, such as the Keystone XL pipeline, the Trans-Pacific Partnership trade deal, and attempted to use rhetoric to distance herself from Wall Street, leaving no room for Biden to maneuver between her and the Democratic socialist to her left, Vermont Sen. Bernie Sanders.

Behind the scenes, groups supporting the campaign made efforts to shore up the support of hand-wringing donors, who during the roughest months of the email saga this summer expressed concerns about whether Clinton was up to the challenge, whether her campaign was up to it, and whether she would be able to stay the course. Clinton allies explained to donors why they thought she had a strong basis and the campaign was not going to falter, and pushed back against any mention of a Biden candidacy, pointing out that it was not clear how Biden would amass the majority of delegates needed to beat Clinton.

Clinton's winning debate performance last week was seen as the final blow to Biden's presidential dreams — his decision not to run was the trophy handed to her as a prize for showing up ready to fight in the debate. Even Biden’s top aides have conceded privately in recent days that Clinton’s performance in the debate was impressive.

“After the debate, no one thought he would run,” said one Clinton ally, who said the campaign’s feeling is that it has turned a corner and that “people are finally seeing the candidate we have all been supporting."

On Wednesday after Biden's decision, Clinton said in a statement: "I am confident that history isn't finished with Joe Biden," and lauded his record as vice president, as well as his "devotion to family, his grace in grief, his grit and determination on behalf of the middle class."