I am not sure if she has officially declared her candidacy or not, as I like to eat, and most 'news' about Hillary makes my stomach sour. Whether or not she has made it official is really of no consequence, as it is clear she is running.
It took about 1.3 seconds for me, and the few sane media outlets, to make a connection between the 'sudden revelations' by Monica Lewinsky in a Vanity Fair article, and the reason for the timing. In the short-attention span theater of politics, this is called clearing the air now, so it doesn't interfere with the Old Dame's run for the presidency. Drag all of the skeletons out of the closet and into the sunlight, and by November of 2016, they will simply be forgotten old bleached bones that won't register on the minds of democratic voters.
I think it is also curious timing, that Chelsea's pregnancy was announced just shortly before the Vanity Fair piece hit the news crawl. If she hasn't already, I am sure that Hillary will use that happy news to steer people away from the Lewinsky line of questioning. A classic, "I don't want to dwell on unpleasant things that happened in the past, I prefer to look forward to a happy future as a grandmother and the first female president of the USA..."
Of course, that spin will be hard to master when people question her about Benghazi. Why should she get to look forward to a happy future as a grandmother, when four men lost their lives and four families are without husbands, fathers, grandfathers? Hillary believes that everyone needs to move on, and that we choose not to be satisfied with the information that has been provided.
I suppose that is the sort of attitude that kept her married to Bill, despite Monica, Gennifer, Maria, Belinda, Naomi, Markie, Patricia, Elizabeth, Sallie, Dolly, and Paula.