I think a good way to analyse the politics of America - and much of the rest of the West - over the past decade or so is on a two-dimensional plot with right vs left as one axis and populist vs what its supporters call technocratic and its opponents establishment politics.
This primary season has given a beautiful microcosm of that - Clinton, Sanders, Bush or Rubio and Trump embody the four quadrants (Left, Establishment), (Left, Populist), (Right, Establishment), (Right, Populist) as clearly as one could hope for.
The obvious trend that becomes clear when viewed on this 2-plot that's much less clear if you only project onto right/left is the rise of populism - six months ago no data-based commentator gave Sanders or Trump a snowball's chance in hell, but in fact Trump has won and Sanders has lost by a much smaller margin than expected.
You can see similar trends across Europe - the rise of Syriza and the Golden Dawn in Greece, the recent runoff between the far right and an ex-Green in Austria's presidential election, the NF in France, the Greens and the far right rising in Germany, a variety of left-wing populist movements and, interestingly, a centrist populist movement (generally the populist centre looks a bit bare) in Spain, and Jeremy Corbyn, the SNP and UKIP here in the UK.
An obvious qualifier to this trend is that, in general, populists haven't risen far enough to win yet - the only one of the examples I've listed who is actually governing a country is Syriza, and to call their rule to date a clusterfuck would be to miss a perfect opportunity to use the word omnishambles. So it's not yet clear how far this tide is going to rise, or if it's going to go some way up and then remain or recede. But, certainly, populism is much less fringe than it was 10 years ago, and the narrowness of Clinton's victory over Sanders reflects that.