ANKARA, Turkey (AP) — A politician who once ran as a presidential challenger to Turkish President Recep Tayyip Erdogan resigned Monday from Turkey’s main opposition party to form his own political movement.

Muharrem Ince, 56, said he was leaving the Republican People’s Party, or CHP, citing foreign policy differences and accusing the party — which was established by modern Turkey’s founder, Mustafa Kemal Ataturk — of abandoning its founding nationalist principles.

Three legislators who left the CHP last week will join Ince’s new party.

Ince was CHP’s candidate against Erdogan in Turkey's 2018 presidential election, getting 31% of the votes behind Erdogan's 53% support.

The politician indicated that he aims to run for president again and has ruled out any possibility of his movement backing a nationalist political alliance that is led by Erdogan's ruling party. The CHP is part of a rival alliance with the center-right Good Party and other parties.

Ince had become a vocal critic of CHP leader Kemal Kilicdaroglu and made unsuccessful bids to replace him as party chairman.