The coalition poised to challenge Nigeria's president in next year's election has received a major boost after prominent opposition figure Rabiu Musa Kwankwaso announced that he was joining.

Kwankwaso, a former governor of Kano state, stated on Monday that he was now part of the African Democratic Congress (ADC) - just a day after resigning from the New Nigeria People's Party (NNPP).

A number of opposition heavyweights have joined the emerging ADC coalition in an effort to unseat President Bola Tinubu's All Progressives Congress (APC), which has been in power since 2015.

Former Vice-President Atiku Abubakar and ex-state governor Peter Obi, two of Tinubu's biggest rivals, have become the face of the ADC.

Kwankwaso ran for president in 2023, finishing fourth, while Abubakar and Obi claimed second and third places, respectively.

However, with so many big names joining the ADC, the major question facing the party is who will be its presidential candidate - an issue that could potentially lead to splits.

On Sunday, Kwankwaso announced he was not only stepping down as the NNPP's leader but leaving the party altogether as the current trajectory of the nation's political landscape necessitates strategic realignment.

I have found it necessary to identify with another political platform that offers the best opportunity to effectively change the nation, he said in a statement.

On Monday evening, he revealed that the "political platform" in question was the ADC, posting on social media: New dawn. We are ADC.

Accompanying video footage showed hundreds of people, many wearing red caps, celebrating at a political rally. A huge poster bears Kwankwaso's face, along with the words welcome to ADC.

This shake-up comes with less than a year until Nigeria's next general election. The ruling party has endorsed President Tinubu for a second term in the January 2027 poll, and he is widely expected to run.

Kwankwaso brings fresh appeal to the coalition and has a large support base in the mainly Muslim northern Nigeria, a key voting bloc in national elections. His followers, known as the Kwankwasiyya movement, are recognized for their trademark red caps and have remained loyal to Kwankwaso through several party changes.

With Nigeria facing significant security challenges, Kwankwaso's past experience as a defence minister offers the ADC a vital rallying point ahead of the election.

Speculation about Kwankwaso's move to the ADC had spread prior to the official announcement, as hundreds of his supporters were seen gathering outside his house, waving ADC flags.

The former NNPP leader also shared photos of himself welcoming senior ADC figures at his home in Kano.

Kwankwaso made headlines in February, following a proposed bill from Republican lawmakers in the US to sanction him over alleged persecution of Christians in Nigeria—claims the government has denied.

The ADC is strengthening its ranks at a time when Nigeria's two main opposition groups, the People's Democratic Party (PDP) and Labour Party (LP), are embroiled in internal crises. The PDP has split into rival factions, weakening its traditional position as the country's largest opposition party.

Under reforms introduced by Nigeria's electoral commission, results from polling stations are to be transmitted electronically in real-time; however, opposition parties have raised concerns about provisions allowing votes to be sorted manually where internet access is unavailable, warning this could weaken transparency.