It looks as if 2015 could turn out to be Europe's Year of the Insurgents. It's going to be a rough ride, and the rise of the insurgents is only one of three major challenges that the continent now faces.
In Greece's elections this Sunday, the left-wing, anti-austerity Syriza party look likely to win. Then in May, UKIP may win enough seats in the House of Commons to play what could be an important role in any post-election cross-party negotiations. And in December, Spanish voters will go to the polls, with the left-wing Podemos group currently tipped to win.
Left-wing? Right-wing? How very last century the terms now sound, with the leader of the National Front in France, Marine Le Pen, openly backing Syriza in Greece. What unites the insurgents is not a coherent ideology but a visceral anger at traditional political elites and the post-2008 political consensus.
Some of the insurgents appeal to voters who have had enough of tolerating ethnic and religious minorities, of open borders, and of supra-national identities. Others aim their anger principally at corrupt political leaders, bonus-benefitting bankers, and a remote EU bureaucracy.
And if Syriza win in Greece on Sunday, they may well provide a huge shot in the arm for other insurgent parties elsewhere. (I somehow doubt, by the way, that Thursday's announcement of a massive quantitative easing programme by the European Central Bank will have much of an effect on Greek voters.)
It doesn't even matter what exactly the insurgents stand for - Ukip, for example, seem to be having terrible trouble putting together a manifesto and have just sacked the man who was meant to be writing one. It's enough for them simply to say to voters: "Look at us. We're not like the rest of them. We're like you."
Now imagine what the political landscape might look like if there's another atrocity similar to the Charlie Hebdo and Jewish supermarket attacks in Paris. What might that do to the strength of ultra-nationalist, anti-immigrant sentiment?
So that's the second major challenge facing Europe: how to react if there are more mass murders on the streets of the continent's major cities. There is, in fact, a precedent: in the 1970s and 80s, the UK, Italy, Spain and Germany faced attacks by the IRA, Red Brigades, ETA, and Baader Meinhof gang respectively, without succumbing to outright totalitarianism. Perhaps that provides us with just a crumb of comfort.
On the other hand, political and intelligence chiefs are now insisting that they need more snooping powers to confront current threats, when we know that the Paris gunmen, just like the killers of Lee Rigby in south London in 2013, were already known to them. What they really need, surely, are more analysts and better systems to enable them to make better-informed judgements about which of their targets are the greatest threat.
That leaves Europe's third challenge: how to deal with Vladimir Putin. His land-grab in Ukraine is a clear attempt to test Europe's mettle at a time when he believes that the continent has neither the will nor the resources to push back. So far, he has been proved right, although the collapse in the price of oil, which is doing immense damage to the Russian economy, may soon prove to be a greater brake on his ambitions than anything Europe or NATO can do.
More than at any time since the end of the Cold War, Europe needs clear, determined leaders who can calm voters' anger and offer reassurance that better times are coming, especially for those who have been hardest hit by the age of austerity. Anger, fear and intolerance of minorities are a highly dangerous mix - we have seen before where they can lead when populist politicians fan the flames. The coming year will be a test that Europe must not fail.