"Will membership of only one political party be encouraged at first, then only that one permitted, that party to be chosen by the government in power?"
That is how it starts, Gilly.
First your social class, political and religious allegiance, sexual bias, and so on are noted so that they can be tools in building a wonderful new society where none of these things will give anyone an advantage over anyone else.
Then someone wants to know your bias and allegiances in a situation where they have no relevance whatsoever to whatever it is you will be doing.
Next your interview is abruptly terminated when you say that you don't see what relevance your politics are to your job selling shoes in the shopping centre shoe outlet.
Then your children come home to say that there will be a camping holiday for members of the XXXX youth group, but only full members can go, and can they join?
Next the XXXX youth group puts on "citizenship" talks. Young members who don't attend these find that they are not picked as office-holders. Senior members get into conversation with them and tell them they were missed at the meeting last week, and remind them that when they joined they did promise to uphold the values of the group, which include regular and prompt attendance. They attend the next "citizenship" talk, which is mostly about how lucky they are to belong to this organisation which is dedicated to raising perfect citizens for the state, unlike certain other groups.
At home the children notice that their parents don't seem quite as enthusiastic about the wonderful new order, and have even been heard to praise one of the "other groups" and to express a preference for a church which is not the established one. At the next meeting the child mentions this to the leader. Their father expects to be promoted this year to a more responsible position, but unaccountably he is passed over for the brother of the leader of the youth group. Mother finds that she is no longer needed at her job so has to apply for benefits. She finds that she doesn't qualify because she is not a member of either The Party or The One True Denomination. Her next-door neighbour cuts her dead in the supermarket.
As for the child's big sister, who would prefer to be a big brother and has been buying illicit testosterone injections on the internet, he/she has been admitted to hospital for emergency oestrogen therapy. Consent is no longer required for this as the area's quota of sex/gender changes (one a year per 500,000) has been reached, so she has broken the law and must return to "normal"
Far fetched?