The alliteration is 'Poison we must purge from our politics'
Explanation:
As a narrow-down, not all alliteration is always together so a good example could be like 'Tim likes Tom' As there are two T's and only one work blocking them off, for me when I write split alliteration I prefer to keep the breaks between 1-2 words long.
I really hope I helped you and have a great rest of your day!! <33