Nigeria's women's affairs minister on Saturday handed in her resignation to President Muhammadu Buhari in the latest setback for his party before presidential polls in February. Aisha Alhassan is the second minister to quit this month. Kemi Adeosun stepped down as finance minister over the alleged forgery of a document exempting her from compulsory national service."Today, the 29th of September 2018, I wish to transmit to the President my decision to resign as the Minister of the Federal Republic of Nigeria and withdraw my membership of the All Progressive Congress (APC)," Alhassan tweeted. In an earlier letter to Buhari, Alhassan said she was resigning from the ruling party because had been disqualified from running for governor in the eastern Taraba state. "I received with shock and dismay that I was disqualified and not cleared to contest," Alhassan said in the letter. "No reason was given for my disqualification Sir."Alhassan said she would back former vice-president Atiku Abubakar - who she called her "mentor" - for the presidency at the next election in 2019 rather than the incumbent.Former vice-president Abubakar hopes to be the presidential candidate for the opposition People's Democratic Party (PDP), which is set to hold presidential primaries later in October. Nigerian politics is largely dependent on patronage, with little to separate the main parties other than personalities.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.