Over the past week, there have been many headlines about "lost emails" from a key IRS figure. This has fed some fears of a possible cover-up in the scandal over the IRS's treatment of conservative groups. References have been made to Watergate and the infamous gap of 18 and a half minutes in one of President Nixon's tapes. Here's what you need to know about what's going on.

What's the background?

In the early years of the Obama Administration, when Tea Party and conservative nonprofits sought tax-exempt status from the IRS, their applications were often delayed for months on end. Eventually, the IRS acknowledged that its screening process — intended to weed out groups focusing on electoral politics, which do not qualify for tax-exempt status — improperly burdened many of these conservative groups with extra scrutiny. Though none of these groups actually had an application outright denied, some conservatives suspected that a White House-directed crackdown on dissenting groups was at work.

But so far, no evidence has emerged that the IRS was acting at the behest of any White House official. And though it's undisputed that many more conservative groups than progressive groups were actually flagged, it has since become clear that the IRS's guidelines also called for extra scrutiny for some groups focused on progressive issues. So the scandal gradually faded from the headlines. Still, Republicans were unsatisfied with the administration's answers, and kept requesting more and more documents.

What are the emails in question?

GOP-led House committees have requested documents from various agencies and individuals since the scandal broke — the IRS says it has already spent $10 million complying with such requests. But particular suspicion has always focused on the director of the relevant IRS unit, Lois Lerner, who was placed on administrative leave shortly after the scandal broke, and has since retired. Though Lerner has repeatedly said she's done nothing illegal, she has twice pled the Fifth to avoid answering questions under oath from Congressional committees. And in May, the House of Representatives voted to hold her in contempt of Congress, because of her refusal to cooperate with the investigation.

Last week, the IRS admitted that many of Lerner's emails were missing

At first, the IRS used search terms to narrow down and provide the relevant Lerner emails to the inspector general and Congress — in 2013, the agency handed over more than 10,000 emails Lerner sent or received. But GOP committee chairs Darrell Issa and Dave Camp weren't satisfied, and wanted to see all of Lerner's emails since 2009. Early in 2014, the IRS finally agreed to supply them all, and set about collecting them — an expensive, time-consuming process. According to the agency, while doing so, it realized that many of Lerner's emails prior to April 2011 were missing, and sought to ascertain why.

Last week, the IRS told Congress of its findings — Lerner's computer crashed in mid-2011, and many of her emails appear to be gone. The agency did manage to reconstruct and supply some of them by pulling them from other employees' accounts — and 67,000 emails that Lerner wrote or received were handed over. But Congressional Republicans were unsatisfied, to say the least, as you can see in this angry statement from Rep. Paul Ryan:

Is there documentation of this alleged computer crash?

Yes. On June 13, 2011, reference first turns up in internal IRS emails that Lerner's hard drive had crashed. In a series of emails afterward, Lerner attempted to get technical help restoring her data — but on August 5, 2011, she was informed that it was unrecoverable.

While this occurred two years before the IRS scandal actually broke, some observers have been suspicious of this timing — because only a short time earlier, on June 3, 2011, House Ways and Means Committee Chair Dave Camp sent a letter to the IRS requesting various documents, including from Lerner's division. The letter mainly focused on whether the IRS was improperly enforcing a "gift tax" on certain donors, but it alluded to broader questions about whether the IRS was acting with improper political bias.

An email chain that the IRS provided to Congress shows Lerner trying to recover her data, and following up several times, saying there were some "irreplaceable" documents there that she needed:

Lerner email to IRS official, 7/19/11: "I'm taking advantage of your offer to try and recapture my lost personal files. My computer skills are pretty basic, so nothing fancy — but there were some documents in the files that are irreplaceable. Whatever you can do to help, is greatly appreciated."

Email from Customer Service Support, 7/20/11: "I checked with the technician and he still has your drive. He wanted to exhaust all avenues to recover the data before sending it to the 'hard drive cemetery.' Unfortunately, after receiving assistance from several highly skilled technicians including HP experts, he still cannot recover the data."

Follow-up email from Customer Service Support, 8/05/11: "Unfortunately the news is not good. The sectors on the hard drive were bad which made your data unrecoverable. I am very sorry. Everyone involved tried their best."

A computer crash wouldn't usually wipe out email — except that the IRS had a policy that only 500 megabytes of data could be stored on the email server at any one time — and that, if this limit was hit, older emails would have to be moved to the employee's computer.

Didn't the IRS back up its email?

As mentioned, Lerner's computer crashed nearly two years before the scandal broke, so those backups would have been long gone by then. IRS employees are also supposed to keep hard copies of some important emails, but, a s Philip Bump of the Washington Post explains here, the policy is vague and it's not clear whether Lerner saved any. It did — but only for six months. After that, the backup tapes were taped over "for cost-efficiency," the agency wrote . (They've since changed their policy.)

What happens next?

More of the same, most likely. Democrats are arguing that this is just the latest mountain-out-of-a-molehill from GOP investigators. But Republicans are more convinced than ever that a cover-up is at work, and some commentators are now calling for a special prosecutor to restore confidence in the process.

Correction: The original version of this piece did not include the fact that, 10 days before Lerner reported her hard drive broken, House Ways and Means Committee chair Dave Camp sent a letter to the IRS asking for various documents related to the IRS, and Lerner's division. We regret the omission and have updated the language of the piece to take this fact into account.

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