Following this, he ran alongside Stewart Dickson in the 2016 and 2017 Northern Ireland Assembly elections, coming 9th and then 8th - but failing to be elected.[6][7]
He than ran again for Mid and East Antrim District Council in the May 2019 local election, this time as one of the two Alliance candidates for the Larne Lough constituency. Donnelly was elected on the first count, polling the second most FPVs in the constituency (1,057 votes) and earning 17.66% of the vote.[8]
Later that year, Donnelly replaced Stewart Dickson as the Alliance Party candidate for East Antrim. He contested the 2019 general election, increasing the Alliance Vote in the constituency by 11.7% and coming second.[9] He reduced incumbent MP Sammy Wilson's majority from 15,923 in 2017 to 6,716.[10]
Member of the Legislative Assembly (2022–)
Donnelly was elected to the 5th seat in East Antrim at the 2022 Assembly election, gaining a seat for Alliance at the expense of the UUP's Roy Beggs, elected, alongside running mate Stewart Dickson, on the fifth stage. He polled 4,224 FPVs, an increase from the 1,817 votes he received in 2017.[11]