THE week began poorly for Jimmie Akesson, leader of the Sweden Democrats (SD), an anti-immigration party that expects big gains in the elections on September 9th. In a television interview with Carl Bildt, a former prime minister, Mr Akesson looked amateurish and ill-prepared. But the SD has run a strong campaign, arguing that immigration drives up crime and puts Sweden’s cherished welfare state at risk. (The country took in more refugees during the migrant crisis of 2015 than any other but Germany.) Polls put the party in second or third place with about 20% of the vote.

“It will be a political earthquake,” concedes Pal Jonson, an MP for the conservative Moderate party. The Moderates lead a centre-right alliance of four parties hoping to unseat the current government, led by the prime minister, Stefan Lofven, a Social Democrat. All parties vow to shun the SD, which makes a majority coalition virtually impossible.

The Moderates think they can win votes from SD supporters who fear the Social Democrats above all. That could allow their leader, Ulf Kristersson, to form a minority government. An unusually high 28% of voters expected to cast their ballots tactically, according to a poll. Leftists, meanwhile, hope that the Greens, who have benefited from the public’s anxiety over huge forest fires this summer, will make up for some of the Social Democrats’ expected losses.

Yet a weak government of either colour may struggle to pass necessary reforms. Sweden faces a housing shortage, but right and left disagree over whether the solution is public housing or ending rent control. To cut immigrants’ high unemployment rate, the right wants to let new arrivals work for below-union wages, whereas the left wants to give them subsidised jobs. The left wants to fix Swedish schools’ worsening performance by re-nationalising the system; the right argues for more private schools.

The SD is often unpredictable on such matters. It backs entrepreneurs on private schools but supports the unions on immigrant wages. For now, other parties are not asking for its opinion. But that may change as its support grows. Anti-immigrant parties have made big gains across Europe, from Germany to Italy and Austria, where they share power. Like those countries, Sweden will find it ever harder to shut the populists out.