With just days to go until the election, a fiercely defiant Hillary Clinton demanded answers about what she suggested is a politically motivated renewal of a previously closed federal inquiry into her use of a private email server at the State Department.
As her campaign scrambled to respond to FBI Director James Comey's decision to notify Congress about renewing the email investigation, Clinton and her top aides characterised the action as inappropriate and irresponsible.
"It's pretty strange to put something like that out with such little information right before an election," Clinton said as a supportive crowd cheered her on and booed when she referred to Comey. "In fact it's not just strange. It's unprecedented and it's deeply troubling."
Clinton's Republican rival, Donald Trump, seized on Comey's letter in an apparent effort to shift focus from his own controversies and score a last-minute surge in a race that even his staff has admitted he has been losing.
Trump called Clinton corrupt and untrustworthy. The Republican said he thinks that some of the thousands of emails that Clinton deleted "were captured yesterday," even though officials do not yet know what is in the emails. He also suggested, without evidence, that there was "a revolt" in the FBI that led to the letter being sent on Saturday.
The Democratic nominee's strongly worded response to the new inquiry signalled a decision to go fully on offence against Comey and confront the email issue and Republican attacks head-on. It signalled clearly the havoc wrought by Comey's announcement - and Democrats' strategy to head off game-changing political damage from a development that had left them sputtering both inside and outside the campaign.
Yesterday, the campaign hastily arranged a telephone briefing with Clinton's top two aides - campaign chairman John Podesta and campaign manager Robby Mook. Podesta does not brief the press regularly.
Podesta described Comey's surprise announcement as "long on innuendo and short on facts," allowing Republicans to "distort and exaggerate" its message. Podesta also sent a strongly worded letter to supporters.
In her appearance yesterday, Clinton stopped just short of accusing Comey, once a registered Republican, of partisan interference in the election. But she did not attempt to conceal her anger. Other Democrats went much further, issuing scathing assessments of Comey's motives and timing, as the potential for new legal jeopardy involving the Democratic nominee roiled an already tumultuous campaign.
The Clinton campaign sent an email with urgent talking points for its high-level surrogates about Comey's "controversial action". Among them was to demand that Comey "immediately provide the American people with more information".
The congressional black and Hispanic caucuses organised a news conference to denounce Comey, at least three Democratic senators drafted a letter of complaint and the Democratic National Committee issued a sharply worded statement. The approach was notable given the kid-glove treatment accorded Comey by Clinton and her campaign before now.
Of chief concern to Democrats now is whether the development, and the uncertainty surrounding it, will cause supporters to disengage or stay home.