Sir Jeffrey Donaldson has announced a bid to become the next leader of the Democratic Unionist party (DUP) and by extension become the next first minister of Northern Ireland. The MP for Lagan Valley said in Belfast on Monday he would square off against Edwin Poots, the agriculture minister, creating the first leadership contest in the party’s 50-year history. Donaldson, 58, paid tribute to the outgoing leader, Arlene Foster, and said he stood for the “politics of persuasion”, a coded reference to centre-ground voters who could decide any referendum on a united Ireland. “We want to build a shared future for Northern Ireland where everyone, regardless of their background, has a part to play in showing the world what we are truly capable of,” he said. Donaldson’s entry into the race gives the DUP starkly different leadership choices at a crossroads for the party and Northern Ireland. The party’s Westminster leader has cast himself as a moderate, unifying figure who could heal fractures in the party and appeal to a broad base of voters. Poots, 55, a young Earth creationist who believes the planet is only 6,000 years old, is rooted in the party’s Free Presbyterian heritage. He is an outspoken critic of the Northern Ireland protocol, the part of the Brexit deal that created a trade border down the Irish Sea, an affront to many unionists that will frame the leadership race. Dissatisfaction with Foster erupted into revolt last week when most of the party’s 27 Stormont assembly members and about half of its eight Westminster MPs signed letters against her. Foster said she would quit as party leader on 28 May and as first minister at the end of June, ending a six-year tenure. She is also stepping down as an assembly member and may leave the DUP. Poots, believed instrumental in the putsch, swiftly declared his candidacy and was endorsed by several assembly members, making him the bookies’ favourite in a contest that will be decided by a few dozen assembly members, MPs and peers. Supporters say Poots already has won over a majority of assembly members, a claim disputed by Donaldson’s side. Donaldson declared his candidacy in the office of Gavin Robinson, an East Belfast MP deemed liberal by DUP standards. He did so on the day Northern Ireland marked its centenary – a hundred years since its foundation and the partition of Ireland. “I am convinced that in this new century Northern Ireland’s best days are ahead of us,” he said. That meant staying in the UK. “Our next century will be built on the politics of persuasion. This will need positive leadership, strategy and values.” Donaldson is believed to have the support of Foster and her Stormont lieutenants but that may be a liability in a party apparently keen on a new direction, starting with a harder line against the sea border to deflect blame for the party’s role in its creation. To become first minister Donaldson would need to sit in the Stormont assembly. Poots’s belief about the Earth’s age prompts scorn and as a minister he has alienated nationalists and the LGBT community, but he is also seen as a savvy, pragmatic politician. If he wins the leadership he plans to split the role of first minister – and earmark that post for an ally – in order to focus on restructuring the DUP. Donaldson started his political career in the Ulster Unionist party as an aide to Enoch Powell and he later defected to the DUP to protest against concessions to nationalists. Since becoming the party’s leader in Westminster his image has softened. The Lagan Valley MP’s leadership bid appears aimed at colleagues who take a wider view of the challenges facing unionism. Catholics may soon outnumber Protestants for the first time and British identity is declining. While 51% of over-65s in the region consider themselves British, just 17% of those aged 18 to 24 feel British, according to a Belfast Telegraph poll published on Monday. Increasing numbers of people identify as neither nationalist nor unionist, a third bloc that could swing a referendum on Irish unity.