 Lahiniriko opposed the constitutional changes proposed in the 2007 constitutional referendum and participated in a national committee that campaigned for a "no" vote as a coordinator of action.Lahiniriko launched a new party, the Socialist and Democratic Party for the Unity of Madagascar (PSDUM), in early February 2007, with himself as its president.He stood for re-election to his National Assembly seat from Betioky Sud district as a PSDUM candidate in the September 2007 parliamentary election; running against him was the TIM candidate, André Avison Tsitohery, who was elected as Lahiniriko's substitute in the 2002 election.