This is the 7951st most frequent Swedish word.
vänsterpartiets
It means "of the Left Party," referring to Sweden's political party Vänsterpartiet.
In this sentence, 'Vänsterpartiets' shows the possessive form of 'Vänsterpartiet,' indicating that the healthcare proposal belongs to the Left Party.
Vänsterpartiets förslag om bättre sjukvård fick mycket stöd.
The Left Party's proposal for better healthcare received much support.
Here, 'Vänsterpartiets' is used to attach ownership of the ideas to the Left Party.
Jag tycker att Vänsterpartiets idéer är intressanta.
I think the Left Party's ideas are interesting.
This usage indicates possession of the success by the Left Party.