Ciudadanos leader Albert Rivera resigned following his party's poor result in the Spanish elections on Sunday.
In the April 2019 elections, the party came third, receiving 4.1 million votes and 57 seats but on Sunday, the party won just 10 seats in Spain's 350-seat congress.
Rivera broke into Catalan politics when he was 26-years-old. His party Ciudadanos or the Citizens party was created as a centre-right, anti-nationalist party.
"We have lost almost half of the votes," Rivera said on Sunday after learning of the unexpected result.
It was instead the far-right Vox party who had a victory, becoming the third most popular party and winning 52 seats.
Prime Minister Pedro Sanchez's party received the most votes but fell short of gaining a majority in congress.
Many political observers expect the country's political stalemate to continue.