At the 1885 UK general election, Ellison-Macartney ran for the House of Commons, and was elected as Conservative member for the newly created constituency of Antrim South.
Hoping to reassert his place in the loyalist hierarchy, Ellison-Macartney led a "law-and-order" campaign, targeted in particular at the violence and agrarian crime committed by William O'Brien's United Irish League [REF].