In a way, Hillary's candidacy is helping her skate past a serious charge anyway. Once her private mail server was found to have contained mail exchanges directly associated with her position as Secretary of State AND it was further found that the messages SHOULD have been marked CLASSIFIED (if not SECRET or higher), a federal felony was revealed. However, nothing much will likely be done about it.
First, no one in the Washington area would dare actually bring charges at this late date in the campaign because it would appear to be politically motivated. If she actually WINS, the whole incident might get swept under the rug forever (or, heck, she could pardon herself). Private citizens can't file the charges because they have no "legal standing" to address the issues. It is a technical charge that would have to be filed by a government official - perhaps from Homeland Security - and nobody wants that level of attention.
Second, as an appointed official, she might not have had direct physical responsibility over the daily actions taken on her server - but her government-assigned system administrator would have to take a particular series of classes (which I myself had to take, since I am also a system administrator for a government department). Those classes would have included a section on the various rules about notifying people when they violate the security principles passed by Congress via the National Secrets Act and associated lesser laws governing treatment of government records. So if someone really got a burr under his saddle, the assigned system administrator would have to take the heat.
Third, Hillary COULD have declared herself as the "classifying authority" for her cabinet-level department (and as Secretary of State, she might actually have been recognized as such) - but there is no evidence that she ever became a CA for the State Department. Only a CA is allowed to downgrade document classification, which is what it would have taken to make the documents legal on that private server.
There is no evidence that the documents were marked properly as having been reclassified to either "For Official Use Only" or "Sensitive but Unclassified" (either of which would have been legal on her private server.) There are strict laws governing how you treat such documents AND how you would mark them to record the fact that they had been "sanitized" for public consumption. The stories that have been published suggest that the laws were simply not followed.
This campaign is almost an exact parallel to the Louisiana governor's race some years ago when David Duke (former KKK Grand Dragon) ran against Edwin Edwards (later to become a convicted felon). We had to vote for either a bigot or a crook. I picked the crook ONLY because I felt we couldn't afford the bigot, and Smiling Eddie Edwards rarely took TOO much off the top. So I picked the devil I knew instead of the devil I didn't know and voted for the crook despite Edwards being a Democrat and Duke being a Republican.