Evil people across the world have found a way to destroy democracies from within: pander to stupid people. Tell stupid people lies that provide simple but wrong answers to complicated questions, and tell stupid people that whatever they wrongly believe without evidence, just because it makes them feel good about themselves, is a valid opinion even though it contradicts what an overwhelming majority of intelligent people have concluded is right.
Yes, I am saying that intelligent people generally know better than stupid people how to run a country, just like they know pretty much anything better than stupid people. That's what intelligence is, per definition: the ability to think hard about complicated matters, learn the facts and understand how things actually work, instead of jumping to conclusions based on nothing but a gut feeling, or something their equally uninformed friends are saying, or prejudice, or envy, or hate.
The only saving grace is that the parties start out as a small group of evil people with a dastardly plan to attract stupid voters to gain power, but when they succeed, they need to find candidates for all the political representation they get, and as these parties grow they tend to get an increasing amount of stupid people as candidates. They end up building a house of cards, because in the long run a party of stupid people will not even succeed in making other stupid people happy with their incompetent rule.
Fortunately, evil people with a brain seem to be a small minority, and they can't even find enough of their own kind to run their political party if it grows to become a major player in national politics. Unfortunately, before these parties fail miserably and are destroyed by their own incompetence, they can do a lot of damage to a country, to its people, to people in other countries, and to the planet. In some cases, that damage is irreparable.
Ruling a country is a difficult task, perhaps the most difficult one there is. It is a job that requires at least a reasonable level of intelligence, and demonstrably stupid people are simply not fit for it. Those who cannot be bothered to seek information, to think, and to find actual working solutions, should not be in charge of anything, least of all an entire country. History is full of examples of stupid leaders, and their reigns always end in disaster.
I hope for the influence of the SD party in Sweden to be short and disastrous. Disastrous to them, not to the country.