evidence: Only three people have held the role of DUP leader since the party was established in 1971 - its founder the late Ian Paisley, followed by Peter Robinson and its current leader, Arlene Foster. [...] On Thursday, Sir Jeffrey told DUP assembly members and MPs that he will contest the next assembly election and serve as first minister if elected. [...] Only DUP members elected to the House of Commons and the Northern Ireland Assembly get to vote in a leadership election, according to party rules.