ABUJA, Nigeria (AP) — Nigerian leading presidential candidate Peter Obi pledged Monday to rid Africa's most populous nation of endemic corruption and widespread insecurity if he wins next month's election.

Obi, who is one of 18 seeking Nigeria’s highest office, described his country as “a failing state” in need of new political leadership during his speech at the Chatham House international affairs think tank in London.

“Unless we change the politics by changing the political leadership, we are stuck in this terrible state of underdevelopment and misery,” said Obi, a former governor of southeastern Anambra state who is the candidate of Nigeria's Labour Party.

Recent polls have shown Obi leading the crowded field, ahead of the ruling party's candidate Bola Tinubu and the main opposition candidate Atiku Abubakar. That’s despite those opponents having high name recognition: Tinubu is a former governor of Lagos state and Abubakar is a former vice president.

Political analysts have described the Feb. 25 vote to replace incumbent President Muhammadu Buhari after eight years in power as a make-or-mar exercise. Since campaigning began late last year, other top contenders have made pledges similar to Obi's: Tinubu has said he is seeking to “renew hope” while Atiku has said he will “rescue Nigeria.”

But observers warn that the exercise is threatened by the security challenges Nigeria is battling, including an Islamic extremist insurgency linked to the Islamic State group in the northeast, rebels in the northwest, and secessionists in the southeast.

On Monday, Obi said he would conduct a dialogue with secessionists in Nigeria’s southeast. And he promised to introduce a range of security reforms, especially in the troubled northern region where thousands have been killed by armed gangs in the last year. Those changes could encourage members of Nigeria’s large diaspora communities abroad to consider returning home and aiding development, he added.

“What you have seen is a cumulative effect of leadership failure over the years which would be solved by good governance. When people start seeing justice, fairness and inclusive government, all those things will start reversing,” he said. “Nigerians are prepared to come back if they can find that they have a country to go back to.”