The letter by FBI director James Comey -- in which he apprised lawmakers of new emails potentially relevant to the investigation of Hillary Clinton -- has prompted lots of second-guessing. But was his letter unprecedented? Clinton herself has said so at a rally in Daytona Beach, Fla.

"Some of you may have heard about a letter that the FBI director sent out yesterday," she said. "It’s pretty strange to put something like that out with so little information right before an election. In fact it’s not just strange -- it’s unprecedented, and it is deeply troubling." (See her remarks here at around 3:30.)

But is it? There’s one prior example that has at least some similarities -- the announcement of an indictment against Caspar Weinberger, the former defense secretary under President Ronald Reagan, just four days before the 1992 election, when Reagan’s vice president, George H.W. Bush, was running for a second term in the White House.

"The bombshell changed the narrative from Bush on the rise to revisiting ghosts of his vice presidential past," wrote Bill Whalen, a research fellow at the conservative Hoover Institution, recently. Reagan biographer Stephen F. Knott told PolitiFact that many Bush aides have told him they believed indictment "stopped a polling trend where Bush was closing the gap."

So was Clinton’s use of the word "unprecedented" justified? Because the two examples are difficult to compare, we aren’t putting it to the Truth-O-Meter. Still, we thought it would be worthwhile to look at both the similarities and the differences between the two cases.

The Weinberger indictment

Weinberger’s case stemmed from the Iran-Contra affair during Reagan’s tenure, which involved the secret trade of arms for Iranian-held hostages and the illegal diversion of some of the proceeds to the Contras, a rebel group in Nicaragua.

Independent Counsel Lawrence Walsh originally indicted Weinberger for misleading Congress in June 1992, but a judge threw out the indictment. Walsh refiled an indictment on other charges on Oct. 30. The indictment concerned notes made by Weinberger at a White House meeting on Jan. 7, 1986, which were "the clearest indication to date" that Bush, then the vice president, "was more familiar with the terms of the arms sales to Iran than he has acknowledged," the New York Times reported at the time.

This indictment was eventually thrown out, too; before leaving office, Bush issued pardons to Weinberger and five others.

But Republicans in 1992 were apoplectic about the late indictment, much as Democrats are about Comey’s letter today.

Some similarities

One obvious similarity is that both examples involve potential criminal activity. If anything, the word used for Weinberger -- "indictment" -- is more powerful than being "under investigation," which was what Clinton faced.

Another obvious similarity is that both developments came shortly before Election Day. In fact, the Weinberger indictment came even later, meaning that the Clinton campaign has a bit more time to recover and press its case.

And a third similarity is that the new development brought back an issue that both campaigns had good reason to think had receded until at least after the election.

Some differences

However, there are also some important differences.

First, Walsh had prosecutorial powers, whereas Comey’s role is investigative. Walsh, unlike Comey, would not have had to involve career prosecutors at the Justice Department in any decision to prosecute.

Second, the linkage of the announcement was more directly perilous to Clinton than it was for Bush. The FBI investigation of Clinton put the candidate herself in legal jeopardy. By contrast, the indictment against Weinberger would, at worst, have theoretically left Bush more exposed to future prosecution by Walsh.

And third, in filing his indictment, Walsh had to spell out in some detail what Weinberger was being indicted for. By contrast, Comey's letter was much more vague, acknowledging that the FBI didn’t know what the emails said or whether they were relevant.

The Clinton campaign emphasized this vagueness, saying it made Comey’s letter "drastically different."

Are the two cases more similar or more different?

Experts we checked with could not come to a consensus about whether the similarities or the differences above were more persuasive.

On the one hand, "a grand jury indictment is a far cry from a vague announcement regarding thousands of emails that Comey has not seen, does not have a warrant to view, and that may or may not be relevant to a pending investigation," said Kenneth A. Gross, a specialist in political disclosure and ethics at the law firm Skadden.

On the other hand, Robert Kelner, chair of the election and political law practice at the firm Covington & Burling, said the 1992 episode "is quite similar to this one, and the fact that it came just days before the election made it much, much worse"

Ultimately, the facts both support and undercut her use of the word "unprecedented." The cases are so different in some details that they can’t be easily compared.