At least a dozen senators were among the 51 All Progressives Congress (APC) lawmakers who walked out on the party to join the opposition People's Democratic Party and the African Democratic Congress (ADC).

Political analysts said the mass defections in the run-up to elections in February 2019 mark a major blow to Buhari's bid for a second four-year term.

Read more: Party split may not bode well for Nigeria's President Buhari

"The APC will now have a very, very large vacuum towards what they will face in the elections. Having about 15 senators leaving your political party overnight is a very big blow that may easily hinder achievement of the party," analyst Sani Yakubu told DW.

The National Assembly in Abuja, Nigeria.

Residents dismiss defections

Many Maiduguri residents dismissed the defections as a storm in a tea cup. Aminu Sule told DW the defectors were being selfish: "Politics requires a lot of calculations. In most cases the most politicians are doing things that are more beneficial to themselves than the populace they represent."

Some APC members admitted that the defections were a blow but said the party would manage to bring back the aggrieved members.

Local APC state lawmaker Muhammad Bello said he was optimistic.

"It is natural for any party in power to have such conflict because you cannot bring people having differences and divergent views and expect them to behave in the same way at the same time," Bello told DW.

"So I don't see any serious challenge but I must confess it is a minus to the APC to have lost such members. But I am optimistic that sooner or later, if not all, most of them will be back in the APC. "

For his part, Buhari told the National Assembly the defections would not affect the party negatively.

Read more: Opinion: Four more years of Buhari? Nigeria deserves better