As the long-time leader of the Social Democratic Party (PSD), Amoussou stood as a presidential candidate in 1991, 1996, 2001, and 2006.

[9] In the first round of the March 2001 presidential election, he placed fourth yet again with 8.6% of the vote, but participated in the runoff when the second- and third-placed candidates, Soglo and Houngbédji, withdrew from the race.

Running against heavily favored incumbent Kérékou, to whom he had previously given his support for the second round, Amoussou received nearly 16% of the vote.

[3][10] By providing token opposition to Kérékou after the President's most important opponents decided to boycott the vote, he gave the outcome a limited measure of legitimacy that it would have otherwise lacked.

[14] Afterwards he was again a candidate for President of the National Assembly, losing to Mathurin Nago of the Cauris Forces for an Emerging Benin in a vote on 3 May 2007.