Any significant political costs are also likely to be fleeting because the revelations came so early in the campaign cycle. It is hard to believe that a lack of transparency in Mrs. Clinton’s use of email will have a significant effect on a general election that will be held some 20 months from now. As the political scientist John Sides wrote on Twitter, “In October 2016, no persuadable voter will be thinking about Hillary Clinton’s email account.” It’s equally implausible that this revelation will draw a second top-tier candidate into the race for the Democratic nomination given the advantages Mrs. Clinton retains over possible rivals like Joe Biden and Elizabeth Warren.

Congressional Republicans will of course continue to investigate the matter, potentially dragging the issue out for weeks or months, but that strategy rarely yields significant payoffs, as we’ve seen in past controversies ranging from Whitewater to Benghazi. While Mrs. Clinton seems to have failed to comply with administration policies and the intent of public records regulations (as well as possibly putting her communications at greater risk of hacking), it is not clear at this point that her actions violated any laws. All of this could change, of course, if a true bombshell emerges from her famous BlackBerry, but she has been under intense scrutiny for more than two decades and is likely to have been extremely cautious.

If there’s one thing we’ve learned from past presidential campaigns, it’s that most supposed game-changers like this quickly fade from the memory of the political class, having never been noticed by most Americans in the first place.