The two major Nigerian parties, All Progressive Congress and Peoples Democratic Party, will, of course, be fielding their candidates:
Muhammadu Buhari 
The incumbent candidate of the All Progressive Congress, Buhari won the 2011 presidential election after defeating former president Goodluck Jonathan. Buhari's ascendance to power was based on his integrity and perceived ability to curb corruption and the Boko Haram  militancy. However, under his watch, Nigeria has witnessed continued insecurity with pastoral conflicts  between herders and farmers as herders from the north move further south in search of arable lands. Also, human rights  have taken a nose drive in his administration, with impunity and corruption at the highest levels of government.
Atiku Abubakar 
Abubakar is the former vice president and candidate of the Peoples Democratic Party. He has tried in the past to win presidential elections but has not been successful. However, his campaign received a major boost with the reconciliation with his boss, former President Olusegun Obasanjo  — who had described Buhari's administration as a failed government. As vice president, Abubakar oversaw the privatization  and sale of hundreds of loss-making and poorly managed public enterprises.
A few other presidential hopefuls to watch are:
Ezekwesili, the only major female candidate in this year's race, served as the minister of solid minerals and later education during the presidency of Olusegun Obasanjo between 1999 to 2007. She was also former vice president of the Africa division of the World Bank from May 2007 to May 2012. Ezekwesili has been at the forefront of the call to rescue about 200 school girls  who were abducted by the Boko Haram militant Islamic group in 2014. She is a co-founder of the #BringBackOurGirls (BBOG) Movement. She is also the presidential flag-bearer of the Allied Congress Party of Nigeria.
Kingsley Moghalu 
Moghalu is a professor of international business and public policy at the Fletcher School of Law and Diplomacy at Tufts University in Massachusetts, USA. Moghalu had previously worked in the United Nations from 1992 to 2008. He was deputy governor of the Central Bank of Nigeria from 2009 to 2014, where “he led extensive reforms  in the Nigerian banking system after the global financial crisis.” He is the candidate of the Young Progressive Party.
Omoyole Sowore 
Sowore is the founder and publisher of SaharaReporters  (SR), an investigative online newspaper. SR has been described as Africa's Wikileaks . This human rights activist is running under the banner of African Action Congress.
The race is on for Nigeria's future
Buhari and Abubakar are the major contenders in this race. Both men have been constants in the political arena in Nigeria. On the other hand, Ezekwesili, Moghalu, Sowore, the “third force”, are a group making their first entry into the partisan political space.
Buhari will be running on the “gains” of his administration over the past three years and must contend with the fact that Nigeria was recently ranked as the poverty capital of the world . The Punch newspaper described Buhari’s “parochial appointments ” as “unprecedented” and has left the country deeply divided. His fight against corruption appears selective and punitive. The recent move  to try the Chief Justice of the Federation — so close to the presidential election — was described by the Nigerian Bar Association as “a pattern of consistent assault  on the heads of the two independent arms of government” by the Buhari administration.
Abubakar, on the other hand, is riding on the “gains” of “multiple lucrative  business interests”. However, he has an uphill task considering the power of incumbency of his major opponent.
Whoever wins the 2019 elections will face enormous challenges like the strengthening the economy , internal security , restructuring power and power devolution , and ethnoreligious  politics.
Editor's note: An earlier version of this post stated that there are 35 presidential candidates and has been updated to reflect that there are 73 presidential candidates.