Labour and Conservatives have selected more candidates for the Blaenau Gwent double by-election.
Labour candidates Owen Smith and John Hopkins
Owen Smith, ex-special adviser to the former Welsh and Northern Ireland Secretary Paul Murphy, will fight the Westminster seat for Labour.
Tories picked Margrit Williams - who works for ex-Foreign Secretary Malcolm Rifkind - for Westminster, and Cardiff councillor Jon Burns for the assembly.
The by-election follows the death of independent MP and AM Peter Law.
Mr Smith, an ex-BBC producer now working for a pharmaceutical company, said Labour faced a battle to win back the trust of local people.
Labour lost the seat, which was its safest in Wales, to Mr Law at the 2005 general election. Mr Law turned Labour's 19,000 majority into a 9,000 majority of his own after he was expelled for fighting the party over all-women shortlists used to pick the parliamentary candidate.
Conservative candidates Jon Burns and Margrit Williams
Mr Smith said: "I do think we lost trust with people last time round. Let's not make any bones about that - that is undoubtedly true."
"But I am confident we can win back the people in Blaenau Gwent because I am confident they are more interested in the future than they are in the past.
An assembly by-election is also taking place in Blaenau Gwent following the death of Mr Law from a brain tumour last month. John Hopkins will be the Labour candidate for the Cardiff Bay seat.
Conservative parliamentary candidate Ms Williams said: "In the last 12 months the people of Blaenau Gwent have shown that they will no longer tolerate being taken for granted by the Labour Party.
Liberal Democrat candidates Steve Bard and Amy Kitcher
"Now, more than ever, they need an effective voice listening to them, understanding their concerns and acting on their behalf."
The Liberal Democrats have chosen Amy Kitcher to fight the parliamentary seat with Abertillery councillor Steve Bard contesting the assembly.
Plaid Cymru will confirm their candidates next Monday, and the Blaenau Gwent People's Voice group is expected to endorse candidates who will stand as independents.