In my lifetime, I can remember this sense of political euphoria once before: May 1st, 1997, when Tony Blair led the Labour Party to a landslide victory. It was a crushing defeat for the Conservative Party that had won four consecutive elections. Tony Blair proved to be far from a perfect Prime Minister, but the Labour Party administration was such a breath of fresh air, and such a change, from what had gone on previously that that was our moment. I have happy memories of a wonderful party in person that night; I will have happy memories of a wonderful party online last night. (However good President Obama turns out to be, he'll be so much better than the alternative in just the same way as Prime Minister Blair was.)
Now the difference between Labour and the previous four terms of Conservatism may or may not be bigger than the difference between Obama and the previous eight years of Bush, I don't know; we shall see, in time. It's not unreasonable to quantify the Obama change as being a more dramatic one by virtue of ending centuries of Presidency by one skin colour; it makes me wonder whether Margaret Thatcher becoming the UK's first female Prime Minister in 1979 was felt to be just as dramatic a change, at the time, by those who loved what she stood for.
The projected resolution of California 8 and Florida 2 is, of course, bigoted, regrettable and offensive, but folk's wonderful words of hope ring true. Defeat prejudice? Yes, we can.