Ulster Unionist leader Mike Nesbitt has announced he is to resign.
Nesbitt had earlier been elected in the Strangford constituency.
The UUP say Nesbitt will remain as UUP MLA for Strangford. He remains leader until his successor is chosen.
With the UUP failing to make any ground on the Democratic Unionists, and losing a number of high-profile seats, the former TV anchor fell on his sword.
His campaign pledge to transfer a second preference vote to the nationalist SDLP appears to have been his undoing, with unionist voters clearly not keen on him voicing support for any candidate that favoured a united Ireland.
Mr Nesbitt said it had been an “absolute honour” to lead the party.
“In pure terms the buck stops here,” he said.
He said his real regret was that Northern Ireland society appeared to have emerged from the election more polarised.
Mr Nesbitt said the electorate had rejected his hope for a post-sectarian vote.
“We will get there,” he said.
“Some day Northern Ireland will vote as a normal democracy. We will vote in a post-sectarian election but it’s now clear it will not happen during the duration of my political career.”
He said that he will remain in position while his successor is found.
Mr Nesbitt had led the UUP since 2012 and pledged to deliver a new middle-ground politics for the people of Northern Ireland.
He attempted to build a cross-community coalition in opposition to what he felt were the failed politics of the DUP and Sinn Fein alliance.
But on a night of disappointments his party lost stalwart former Stormont minister Danny Kennedy as well as other senior members and failed to close the seats gap with the Democratic Unionists.
Mr Nesbitt led his team out of a five-party Stormont powersharing administration which included Sinn Fein following a 2015 killing by members of the Provisional IRA.
The nationalist Social Democratic and Labour Party (SDLP) joined him after last May’s Assembly election.
Mr Nesbitt attempted to build a coherent Opposition at Stormont and invited youthful SDLP leader Colum Eastwood to his party conference last year.
He said: “Vote me, you get Colum. Vote Colum, you get me.
“Vote Colum and me, and you get a whole new middle-ground politics, dedicated to making Northern Ireland work, whatever our motivations.”
The Assembly election uses proportional representation voting and in an effort to signal his intent Mr Nesbitt said he would transfer his vote to the SDLP candidate.
Traditionally unionist ballots have transferred to other unionists and senior Ulster Unionists voiced disquiet about Mr Nesbitt’s breach with custom.