My bold, and please forgive what could be seen as pedantry, but the all-too-common misuse of this word, so beloved of journos and politicos, is a bête noire of mine. As nobody on the planet has claimed that Gove is the Prime Minister then your description cannot apply; he could be called a potential PM, or a prospective PM, but not a putative one.
It has started here and on my twitter after just a few minutes of the beeb broadcast. The total sense of fear being spouted by remoaners at the prospect of Boris being PM. Vote him in now !! Heads are waiting to explode