The move is not unprecedented. A few times in the 60's and 70's the medical condition of politicians were either leaked or hacked and then released to the world. Almost immediately, it caused the candidate to drop out. This has also been the case even with spouses of political candidates. After one particularly nasty barb set at the wife of a candidate, a truce was declared, at least at the Presidential level. It was completely unwritten, but big jaw dropping medical conditions were taken off the table. Nothing was released, and all that anyone could do was to wildly speculate and make a lot of charges, but the actual release of anything was considered in poor form.
This time around though, it appears that unwritten rule is seriously being considered as something to be broken. The crazy thing is, it appears that it is going to be broken about someone who really has no shot, at least looking as things stand now. Even though they have previously run for the office, they didn't make it out of the preliminaries, and there is nothing to suggest they would be able to pull it off again. There are multiple other people from that state, who would get far more interest and money and votes.
So, the question is why now? It would have made much more sense the last time they tried. Everyone knew then what they know now. Nothing has changed. It would have been a much more devastating outcome last time they ran because it could have affected who came out of the preliminaries. This time, it would do nothing but cause pain and embarrassment. Why? To stop them four years from now or eight years from now? Does someone know something about this time around that no one else does? There is no way any of the front runners would pick the person as the number two. It wouldn't make any sense. It adds nothing. So, why the buzz that this information is going to be released? Is it a threat to back the person off from running?