It's not really unprecedented or unique though is it. There's currently a sea-change going on in large chunks of global politics.
So let's take a quick trot through Europe for an example. One of France's two main parties since the 70s (the Socialists) got 7% in the last Presidential election! And that's from having the sitting President to irrelevance in one day. So they actually polled less than one of the minor parties on the far left. France is now governed by President Macron and a brand new party that he created to support him (Republique en Marche) - which aligns with the Liberal Group in the European Parliament - not the socialist one). With the old centre right party in opposition but the main presidential candidate again coming from the far right Front National - although they changed their name after losing that election. But they'd also been the run-off challenger in 3 of the last 4 presidential elections.
In Spain we've had a 2 party system since the 70s when the dictatorship ended. The socialists finally manged to cobble together a coalition after a couple of elections, but it's no longer a 2 party state with some minor regional parties as there are now 2 new boys on the scene polling not much less than the old main parties. Podemos on the far left and Ciudadanos who look more like liberal / centre right party.
Italy has just been governed by a coalition of the 5Stars (less than a decade old and created by a TV comedian with a conviction for manslaughter) and the Lega Nord - which 15 years ago was a minor far right regional party. The Italian Socialists (main party since the war) were beaten into 3rd place but are now in coalition with the 5 Stars - to keep the League from what looked like winning an overall majority. And the old Christian Democrat rump, in almost constant government since the war, merged with Berlusconi's lot 20 years ago now languish in an irrelevant fourth place, at under 10%
Greece's old Socialst party, again in constant government since the end of the dictatorship, virtually ceased to exist and was replaced by Syriza - which used to be an irrelevant minor far left party. The New Democrats survived though as the centre right party.
In Scandinavia we have a whole bunch of populist / far right parties getting to the edge of power and/or being held off by increasingly difficult coalitions of everybody else. So we have the Finns party - who actually got into coalition and have also been the main opposition. Then there's the Sweden Democrats who've got similar levels of support. And in Denmark we have Danish People's Party - which has propped up a government and not joined in.
I'll finish my list in Germany, as the post is getting long. We've had Merkel as Chancellor for a long time, with a coalition of the two main parties for the last decade - so on the surface it looks quite stable. But change is a comin'. Partly because she's said she won't stand at the next election. But also because that coalition is a sign of weakness for the two big parties. They used to be big enough to govern with one smaller party - but again, German politics is moving fast. AfD coming up on the far right and Die Linke on the far left are both polling about 10% and the SPD (socialists) are now polling below the Greens - who were traditionally their junior coalition partner.
In the whole of Northern and Western Europe the socialist / centre left parties have really been hammered in the last decade - often virtually ceasing to exist and being replaced by far left parties - or being forced into coalitions with the centre right to keep out the further right. It's a bit more mixed on the cenre right, but they've often been pressured by parties further to their right to either join them, or head into the centre to keep them out.
There's a lot of people voting for overtly nationalist parties nowadays. Most of them being quite populist too - often being culturally conservative but economically left wing.