This confirmed opinion polls that Syriza was the party with the strongest support since national elections in June 2012. Syriza is opposed to the austerity program imposed on Greece in 2010 but is not anti-European Union. Golden Dawn is against austerity but also strongly against the European Union. The two parties represent the often bloody historical divide between Greece’s left and right and would never agree on anything besides attacking the government.

Greece is not the first country to witness a protest movement against economic austerity, nor the first where xenophobic extremists have made their presence felt. But nowhere have the two extremes grown so influential so quickly, as formerly fringe groups fed off voters’ anger and insecurity and wore down the credibility of mainstream parties.

In national elections in 2009, before the crisis, Syriza won just 4.6 percent of the vote, while Golden Dawn barely registered, with 0.3 percent (just 19,624 votes). But their recent strong showing, and the coalition government’s weakening, suggests that if these had been national elections the results would have rendered Greece ungovernable, as no party could have formed a viable coalition with any like-minded group. With the economy still on life support, such political instability would be devastating.

The popularity of extremist groups not only undermines the political system’s cohesion but also threatens their own future: Thrilled by the success of their simplistic rejection of the state of things, these parties are unwilling or unable to compromise. They will either remain on the fringe or tear themselves apart. It’s the existence of a government with unpopular policies that in part empowers them. After six years of recession and four years of austerity in Greece, Syriza has been unable to break through the ceiling of 26.9 percent that it won in 2012, while the coalition has not fallen so far as to make governing untenable. The political system limps on.

The aggrievement and disillusionment that fuel such extreme movements can arise from real causes or perceived ones. People may feel fear and deprivation because of the impact of recession, unemployment and higher taxes. They may feel threatened by immigration, or by the idea of immigration. Nationalism can be provoked by outside factors, such as a belligerent neighbor or a sense of national humiliation and loss of control.