Rem Rieder

USA TODAY

On Friday, just three days before the hotly contested Iowa caucuses, they were back in the spotlight:

Hillary Clinton's emails.

It is a story that comes and goes, but it is a story that by no means is going away anytime soon.

The FBI investigation into Clinton's totally misguided decision to use a private email server while she was secretary of State remains a ticking time bomb that could blow up Clinton's quest for the Democratic presidential nomination and the keys to the White House.

Which is not to say that it will. There may not be any developments or revelations serious enough to derail the Clinton campaign. And when it comes to dodging bullets, to skirting danger, to surviving, the Clintons have few peers.

The thing is, nobody knows.

Friday's development was the last thing Hillaryworld needed.

37 pages of Hillary Clinton emails withheld as 'top secret'

The Obama administration announced Friday that 22 emails making up seven email chains that passed through Clinton's private server had been classified "top secret" and would not be made public along with Clinton's other emails. It was the first disclosure that top secret material had been on the unsecured server.

Clinton has maintained that she didn't send or receive email that was classified at the time, and that was the case with these emails. The "top secret" status came later. But their existence underscores the colossal irresponsibility for a secretary of State to use such a system. Inevitably material will show up that has no business being on an insecure server.

After stubbornly, and ludicrously, defending her use of the private email setup, Clinton in September at last conceded it was a mistake and apologized for it. But in her response to the latest development, she has sought to cast the controversy in a political context: The Republicans are trying to undermine me with it, a la Benghazi.

Vast right-wing conspiracy, anyone?

Clinton compares e-mail questions to Benghazi

One of the problematic aspects of the email mess for Clinton is that it brings out one of her worst characteristics, Under fire, cornered, she reacts defensively, legalistically, sarcastically. Which simply aggravates what's a serious issue for her: Lots of people don't trust her and consider her dishonest.

When she's snarky, she's not really likable enough, President Obama to the contrary.

Rieder: The lessons of Hillary's press debacle

The issue also changes the subject, forcing her to respond rather than pursue her own agenda. And no matter how you parse it, the decision to use the private server raises serious questions about her judgment, and they return to the fore every time the emails pop up.

But the true wild card is the FBI investigation. The Washington newspaper The Hill published a story last week saying the decision on whether to press criminal charges against Clinton or her aides could come right in the midst of the general election campaign, a prospect sure to be causing plenty of agita for Democratic loyalists.

The email albatross hasn't figured prominently in the Democratic primary thus far because Clinton's chief rival, Vermont Sen. Bernie Sanders, has stayed away from it. Sanders has stressed that he wants to focus on issues like income inequality and not resort to personal attacks.

At a debate in October, Sanders famously declared, "The American people are sick and tired of hearing about your damn emails." Over the weekend Sanders refused to take the bait from journalists and belabor Clinton over the latest email fracas. But when asked Sunday by CNN's Jake Tapper if that meant he thought the email affair was no big deal, the senator responded, "Nope, nope. That is not, I think, a fair assessment. That is, I think, a very serious issue."

If Clinton wins the nomination, she is not likely to encounter an opponent quite as bashful. Assailing Clinton has been a popular Republican sport for years. During this year's GOP primary, the Republican combatants often have been at least as eager to attack Clinton as their Republican opponents. And with the private emails Clinton has presented her foes with a powerful weapon.

In a preview of coming attractions, the Republicans were quick to seize on the latest email development, with Donald Trump asking via Twitter "how can someone with such bad judgement be our next president?" and Marco Rubio proclaiming it a "disqualifier" for Clinton.

So if you are sick and tired of hearing about Clinton's damn emails now — just wait.

Follow USA TODAY columnist Rem Rieder on Twitter @remrieder