I didn't see the presidential debate last night, but there seems to be a considerable confusion over who 'won' it; I have seen a considerable amount of angsting, and a considerable amount of bravado, from both sides, while a look at the actual polling numbers in response to the debate gives an equally muddled view. Now, the first thing to grasp is that the purpose of political debates (and any other debates not in actual debate contests), at least in principle, is to inform, not to 'win', and it's very hazy to determine what counts as a 'win' when you have no scoring system for the debate itself. But the general idea of 'winning' a debate is that of whether it left good or bad impressions on those it reached, by and large, and that, while still slippery, is less hazy. I re-post the brief discussion below, from 2004, about the way in which who 'won' is a soft fact that depends on things that happen after the debate. This is actually, incidentally, one of the reasons Hillary Clinton has always done well in debates; she's one of the few politicians today who grasps the fact that a debate is less about what what you say and do and more about the what it lets you give your supporters to hammer the other side with until the next debate -- it's one of the things that made her stand so well against Obama, who is a far better speaker but who also kept being outmaneuvered after debates. (As I said, I didn't see the debate, but the fact that Clinton supporters are slow with coming up with any such hammers suggests that her performance was unusually weak, and that she may have made the error of covering old ground rather than giving her supporters something new to work with. But, of course, nothing but time will tell.)
By 'soft fact' I do not mean the sort of excuse for a fact that often passes in politics. I mean instead a technical term in philosophy of time: a 'soft fact' is a fact some of whose truth conditions occur only after the fact itself. If we think of evaluations of good and bad as being factual evaluations, we can see some rough examples of the sort of thing that's meant. For instance, if something happens that radically changes your life, it can often be uncertain until other things happen whether it was a bad happening or a good happening. Indeed, it might sometimes be the case that what seems bad at the time turns out to be one of the best things that has ever happened to you, or vice versa, because of what comes after.
I think it's important to recognize that in a certain sense, who wins or loses a presidential debate is a soft fact; we cannot, strictly speaking, determine the matter until well after the debate because the fact of the matter is, as it were, still pending. When we think of who 'won' the debate these days, we usually have in mind who appeared better to those who watched the full debate. However, the television appearance at the time is not everything that needs to be kept in mind when judging whether the debate was won or lost, because it is not the only medium in which the debate reaches people. There is, of course, the radio version at the time, and that can give different impressions; there are also the transcripts on the internet, and reading can potentially give yet another impression of the debate; and there are radio and television clips, and newspaper summaries, afterward. All of these, even the things that are reaching people well after the debate itself is actually over, are as it were the debate itself, still propagating through society. In addition, memories of the debate fade and change as other things happen (e.g., something that might not seem annoying in one debate might become annoying if it occurs in all the debates, thus adversely affecting judgment of the first debate). There are a lot of factors that need to be kept in mind. Who wins or loses the presidential debate actually depends on the sum effect of all this. Things can get surprising. It is how the debate affects the whole race that determines who won and who lost; victory and defeat in a presidential debate is a soft fact. This is not primarily 'spin' (although certainly there's always that) but is due to the simple fact that presidential debates have effects that are much more extensive than just the first impressions of television viewers (or radio listeners).
I suspect there are lots of soft facts in politics, even of the technical philosophical kind....