Donald has heard of campaigners for O'Donovan dotted around the place, and you need to beat the crap out of them in the allotted time to give Donald an electoral edge.
Have a Fight
These campaigners have aligned themselves in a straight line across the island. The nearest campaigners is atop the AMCO HQ in Bedford Point, the near-further campaigners around Belleville Park, and the farthest campaigners around Liberty Campus. Once you've "disbanded" all of the campaigners, you're aim is accomplished.
You will get a call from Salvatore, reopening his missions. You will also open up the Church Confessional missions.