Но другая часть общества в ужасе от того, что он может вернуться

[Transl]

(о выборной кампании - не у нас).

[foxtrot]

consider:
But the other half of society is gripped by the fear he might come back/anticipating his possible comeback

[Аристарх]

Без контекста
Another/the other part of the society is horrified by the idea that he may come back/his potential coming back/returning.
Это если речь о человеке

[суслик]

как вар.: the idea of his potential comback would cause fear/utmost anxiety/great concerns in the other camp