Between 1978 and 1982, he taught dentistry at the Universidad Nacional Federico Villarreal, and he simultaneously served as national secretary of popular urbanizations within his party.
[6] On October 27, 2019, Trelles was elected president of the Peruvian Aprista Party, defeating former congressman Carlos Roca Cáceres.
The leadership election was controversial, with accusations of fraud and favoritism towards Trelles' list, which involved former congressman Mauricio Mulder, as chairman of the Political Commission, and current secretaries-general Elías Rodríguez and Benigno Chirinos.
[7][8] His accident was brought to light by the losing side, as they suggested that Trelles was not even aware of him running for the position due to his medical condition.
Pundits view his election as an intent by Mulder, Rodríguez and Chirinos to continue manipulating the party's leadership, as the presidency is a more honorific position for the late Alan García.