The migrant crisis, which is now seeing some 1,500 asylum seekers arrive in Sweden each week, has not just shaken the country’s infrastructure. The country’s party system is in havoc, with the xenophobic Sweden Democrats setting the political tone and occupying an ever-stronger position with each passing week. The government itself may be in danger if the Greens, the ruling coalition’s junior partner, decide they can no longer stand by as policies they oppose get implemented.

“Right now there’s a whole lot of ad hoc and rapid changes in Swedish politics,” said Tommy Möller, a professor of political science at the University of Stockholm and an expert on the country’s political party system. “Even just during the past several days the language used by the political parties has changed. Things that used to be unthinkable are now thinkable. And there’s a race between the Christian Democrats and the Moderates to adapt themselves as much as possible to the Sweden Democrats’ policies while at the same time distancing themselves from the party.” The November 14 Paris attacks provided the party with new ammunition for its calls to limit immigration, and representatives including Ted Ekeroth—the party’s leader in the southern city of Lund—took to Twitter to essentially say “I told you so”.

The Christian Democrats and the Moderates belong to Sweden’s reliably centrist right wing, which formed the government until the most recent elections, in 2014. But as far as large chunks of the public are concerned, traditional parties such as the Christian Democrats and the Moderates, and indeed the Social Democrats—for decades Sweden’s predominant party—are no longer an attractive choice. Instead record numbers of voters support the far-right Sweden Democrats, who more than doubled their support in last year’s elections, becoming parliament’s third largest party, and have since gained even more support. A poll last week placed the Sweden Democrats as Sweden’s most popular party, with 26.8 percent of voter support.  (Another new poll gives the party 18.3 percent voter support, which is still a leap from the 12.9 percent of votes it received in the 2014 elections.) And in a recent ranking of Sweden’s most powerful personalities, the Sweden Democrats’ leader, 36-year-old Jimmie Åkesson, came third, after Prime Minister Stefan Löfven and Central Bank head Stefan Ingves.

But the traditional parties refuse to work with the Sweden Democrats, and Löfven has called the party neo-fascist. The presence of the ever-more popular pariah, combined with the dramatic influx of asylum seekers—the Migration Agency projects 190,000 asylum seekers will arrive this year, up from 82,000 last year—is causing turmoil in traditionally consensus-oriented Swedish politics. “The Sweden Democrats have long argued that immigration is taboo, but now that everybody else is talking about it, they have to resort to even stronger actions,” explained Andreas Johansson Heinö, a researcher at the Stockholm think tank Timbro. “That’s why they’re proposing a referendum on immigration.” In addition, most of the traditional parties are now trying to slash the flow of asylum seekers—a move also long demanded by the Sweden Democrats.

Despite their small ideological variations, traditional Swedish parties have kept being elected thanks to their positions on three issues that are hugely important to voters: education, healthcare, and social welfare. “In general, all the parties except the Left Party [which won nearly six percent of the votes in the 2014 election] and the Sweden Democrats pretty much agree,” noted Joakim Ruist, an economist at Gothenburg University who studies public attitudes to immigration. And that’s exactly the problem: by representing a narrow scope of opinions they have created a vacuum for the Sweden Democrats, who may represent popular opinions but often take elected office lightly and have office-holders with plainly bizarre views. Recently a local SD politician warned that children born to a Swedish and an immigrant parent will have lower IQs than other Swedish children.

Now the Sweden Democrats are upping the ante. In addition to proposing the referendum, the party has announced it will be taking politics to the streets, prioritizing public acts over parliamentary maneuvers. “It’s not as if they’re going to boycott the parliament,” said Möller. “But nobody knows what the result will be.” The party, represented by at least one of its MPs, has already begun distributing flyers to refugees on Lesbos, warning them against coming to Sweden, where there is “no money, no jobs, no homes”. The flyers are signed “the people of Sweden”.

To those accustomed to the bellicosity of U.S. politics, the Swedish turmoil may seem mild indeed. But the Sweden Democrats’ success is destabilizing Swedish politics at the very moment when the migrant crisis is creating political instability of its own. The Green Party, the junior partner in the Social Democrat-led coalition, has long opposed the very policies—including attempts to restrict asylum seeker numbers—the coalition has now introduced. “It’s very possible that the Greens will leave the coalition,” explained Möller. “They started out as a party based on the peace and environment movement, and in recent years they’ve fought very hard to be seen as a responsible party, but they have already made very painful concessions. The question now is where they’ll draw the line.”

If the Greens were to leave the government, Löfven would face tricky choices. Among them: forming another minority government, this time with a couple of center-right parties as his coalition partners. If he pulls this off, and is able to push through more initiatives that move closer to long-held Sweden Democrat positions, the levee will probably hold a while longer. If not, Sweden could be sailing into choppy waters.