GRONINGEN, Netherlands — Set aside, for the moment, the surging far-right leader Geert Wilders or the incumbent, liberal Mark Rutte fighting to hold on to the prime ministership.

The other big story of the Dutch election next month is the collapse of the mainstream left. It goes a long way to explain why this country's politics are in such turmoil.

Heading into the March 15 poll, low-income voters are souring on Labor, currently the second-largest party in parliament, and migrating to the far right and a smattering of far-left parties.

Polls indicate the Labor party (PvdA) could slip as low as seventh place in the election, abandoned by past voters who say they sold out their left-wing beliefs in the five-year-old government coalition with Rutte's conservatives.

"I’m talking to the voters — and talking with urgency," PvdA leader and Deputy Prime Minister Lodewijk Asscher told POLITICO, adding, with the understatement of a politician being punished for the current political direction: “There’s room for improvement."

Frustrations over economic inequality in the wake of the 2008 global financial crisis, slowing social mobility and rising health care costs are driving voter flight from Labor. Eager for change, they're punishing the party for having signed off on budget austerity in their time in power. Like elsewhere in Europe, there is also a general sense of malaise and anger at seemingly out-of-touch elites.

Lower income voters are especially angry, said Asscher. "They have felt most of the crisis," he said. "We have to find a solution for that, rather than telling them it’s all somebody else’s fault."

The party’s predicament isn't unique. Elsewhere on the Continent, far-right parties have managed to siphon off large parts of their traditional voter base with an anti-immigrant message combined with promises of lower taxes, state welfare protections and generally a return to the good old days.

In the Netherlands, Asscher recently called for restrictions on the movement of workers within the EU, in an attempt to protect wages and win back parts of the party's core support. At the same time, Labor defends its marriage with Rutte’s People's Party for Freedom and Democracy, arguing their policies have been vindicated by a return to economic growth. It urges voters to rally around it to stop the advancing populist forces that have upended the political order elsewhere in Europe and the U.S. “There’s a populist wave all across Europe and the world," said Asscher. "And we should not let that happen [here].”

Rising inequality

Part of the challenge is that on the hot political issues — immigration and the European Union — the Dutch electorate has become starkly divided along income and educational lines.

There are a lot of undecided voters in play: A full quarter of voters who chose Labor in 2012 were unable to name any party of preference when surveyed by Kantar.

The gap between rich and poor has widened in the Netherlands since the global financial crisis of 2007-2008, continuing a trend that began in the late 1970s, with median household income stagnating, according to WRR, the Netherlands' Scientific Council for Government Policy.

The Dutch government responded to the financial crisis with austerity, introducing tax hikes and spending cuts, causing ire towards the Labor party, a traditional defender of the welfare state.

In municipal elections in 2014, Labor bled seats.

Ton Heerschop, a local councilor and election candidate in the southern Dutch province of Limburg, where his left-wing Socialist Party has increased its local seats, said it was clear they were picking up alienated Labor voters.

"Labor isn't Labor anymore," he said.

Health care is the No. 1 issue cited by voters, according to both Ipsos and Kantar. There is anger over the steep rise in the cost of so-called "compulsory excess payments" — the amount, set by the government, that patients pay before insurance kicks in — which has jumped from €150 in 2008 to €385 this year.

“People are afraid the traditional welfare system is collapsing slowly but surely, and they make a connection with immigration and globalization,” said Kantar’s Tim de Beer.

“The lower-educated are increasingly negative about immigration, and the higher-educated are increasingly positive" — Matthijs Rooduijn political sociologist

There are a lot of undecided voters in play: A full quarter of voters who chose Labor in 2012 were unable to name any party of preference when surveyed by Kantar.

“Of course, those people might come back [to Labor], but I seriously doubt it,” De Beer said. “Labor are in a really nasty situation now."

Immigration divides voters

Immigrants account for under 10 percent of the Dutch population, according to Eurostat, ranking it near the middle compared to other countries in the EU. But Wilders has made it a successful issue for his Freedom Party (PVV), espousing a fiery anti-Islam rhetoric that appears to appeal to voters.

“The lower-educated are increasingly negative about immigration, and the higher-educated are increasingly positive,” said political sociologist Matthijs Rooduijn.

Though Wilders is likely to be rewarded with a chunk of support from Labor’s disaffected base, voters are also going to other parties on the left, including GreenLeft, the liberal Democrats 66 and the Socialist Party.

“It depends on what is most important to the voter. If they are worried about immigration, they might vote PVV. But if they are most interested in the welfare state, they might come to us,” said Peter Kwint, an Amsterdam councilor and Socialist Party candidate.

Kwint, however, cautioned that the Labor party has a history of late comebacks. “I’ve been through enough elections to know not to write them off,” he said.