Sir Jeffrey Donaldson has declared his candidacy to lead the Democratic Unionist party (DUP) and said he will seek to unite Northern Ireland’s unionists in a campaign against the Irish Sea border. The Lagan Valley MP made the announcement on Monday, confirming his status as the favourite to replace Edwin Poots, a short-lived leader who resigned last week after an internal revolt. Donaldson said he would work to restore confidence and faith in the DUP, which is reeling from infighting, and reach out to other unionists. “Now, more than ever, we need to unite in the face of the threats posed to Northern Ireland by the protocol. Make no mistake, this is the number one issue facing our country, our people and our place in the United Kingdom.” If no other candidate emerges – nominations close on Tuesday – Donaldson is expected to be coronated as leader of Northern Ireland’s biggest party on Saturday. Donaldson defined the job as leading opposition to the post-Brexit checks on goods travelling to Northern Ireland from Great Britain, which some unionists consider a threat to the region’s economy and British identity. “If elected, I will ensure that the government doesn’t just listen, but recognises the need to take decisive action to deal quickly with the protocol. A failure to act will undoubtedly have consequences for the stability of our political institutions and the prosperity of our economy.” The statement did not call for the protocol to be abolished – in contrast with some other unionist and loyalist leaders. Nor did it threaten to topple Northern Ireland’s power-sharing assembly, which some unionists say is the only way to win concessions from the British government and European Commission. DUP convulsions have destabilised the assembly and executive at Stormont and raised the prospect of a snap election. A Donaldson coronation may calm the region’s febrile political mood, at least in the short term. Arlene Foster stepped down as DUP party leader after a putsch in April fuelled by grassroots anger at the sea border. Poots, a Stormont agriculture minister, narrowly beat Donaldson in a two-horse succession race last month. After just 21 days in the job Poots quit as party leader last week after a party revolt over a deal on Irish language legislation, which colleagues viewed as a victory for Sinn Féin. The rebellion also undermined Poots’s protege, Paul Givan, just hours after Givan’s nomination as first minister. The DUP reportedly wants Givan to step down once a new leader is elected. Before taking the post of first minister Donaldson would need to resign his Westminster seat and be elected to Stormont, a process that could take months. In the meantime, he could appoint a party colleague to replace Givan. Donaldson, 58, is regarded as a relative moderate within the DUP. He started his political career in the Ulster Unionist party as an aide to Enoch Powell and later defected to the DUP to protest against concessions to nationalists in the 1998 Good Friday agreement. Since becoming an MP his image has softened.