Abuja -The powerful head of Nigeria's Senate, Bukola Saraki, on Thursday announced he would run in February's presidential elections against incumbent Muhammadu Buhari.
The move, by the country's third-highest politician, ratchets up the challenge facing Buhari and increases the electoral uncertainties in Africa's most populous nation.
"I hereby announce my intention to run for the office of President of the Federal Republic of Nigeria in the coming general elections in 2019 on the platform of the People’s Democratic Party (PDP)," Saraki said at a meeting with young people in Abuja.
"I do so with the firm conviction that I have what it takes to secure inclusive growth for Nigeria and Nigerians."
Saraki, 55, was born into one of Nigeria's wealthiest and most politically prominent families.
Ranked in Nigeria's political hierarchy behind Buhari and Vice President Yemi Osinbajo, Saraki has long been seen as having his sights on the top job.
In recent months, he became linked to a string of defections that appeared to be aimed at weakening Buhari.
On July 31, citing irreconcilable differences, he quit Buhari's All Progressives Congress (APC) and returned to his old party, the PDP.
During his time as president of the Senate, Saraki has had a running battle with the government.
He ran into legal problems that he said was because he had been marked out as a critic and rival by the presidency.
He was accused of flouting parliamentary rules to secure the position, of failing to disclose all his assets during his time as governor and of having links to a gang that carried out a brutal armed robbery in Kwara state that saw 33 people shot dead.
Buhari, elected on an anti-graft ticket, has been accused of using his fight against corruption to crack down on perceived political opponents.
Many political figures, including former national security adviser Sambo Dasuki are languishing behind bars despite several court orders for their release.
- Under pressure -
Buhari, a former military dictator in the 1980s, was elected in 2015.
He has announced his intention to seek a second term. He has the support of the APC's senior ranks, although a primary is required.
But the 75-year-old is under intense pressure to stand down on account of his age and failing health and faces criticism for his handling of the Boko Haram jihadist insurgency in northeastern Nigeria.
The president came under fire Tuesday from the opposition, lawyers and civil society groups for saying "the supremacy of the nation's security and national interest" was above the rule of law.
Buhari should be made to "answer for the litany of human rights violations in Nigeria, including documented disobedience to court orders, extra-judicial and arbitrary executions, unlawful arrests and political detentions," the PDP said.
- Primary boost -
On Wednesday, another heavyweight candidate said he would run in the PDP primaries -- Rabiu Kwankwaso, a former aide to Buhari and ex-governor of Kano province, who defected to the PDP in July.
Mainly Muslim Kano, home to 15 million out of Nigeria's population of around 180 million people, was a vital stronghold for Buhari in the 2015 elections.
Other power-players who have bolted from the APC are the governor of Ekiti state, Ayodele Fayose, and former vice president Atiku Abubakar.
"The biggest challenge now for PDP is to organize free, fair, and credible primary elections," said political analyst Chris Ngwodo.
If this can be achieved, the opposition will seize the limelight, he suggested.
"The primaries will be very competitive, and then capture public attention. All the excitment and all the dramas will be within PDP."
Buhari had begun the year as favourite for the elections, facing an opposition that was disorganised and weakened by the fight against corruption.
But, said Ngwodo, "I do suspect that for the president, (2019) will not be as easy as 2015."
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