The euphoria at the rally is palpable. Speaking to the cheering crowds, Buhari promises to clean up the country, which in 2015 ranks 136 out of 167 countries on the Corruption Perceptions Index.
Government corruption – in the form of bribery, waste and siphoning off contracts is rampant in Africa's biggest economy. But Buhari is even seen by his political opponents as incorruptible – a sensation in Nigeria.
During his visit to Kano, Buhari stops to pay a visit to the Emir of Kano, the Muslim head of the region. But so many people storm around Buhari's party bus in the hope of catching a glimpse of the presidential candidate that he's unable to get out of the vehicle. Amid scenes normally reserved for pop stars, Buhari has to turn back.
Two months later, Nigeria goes to the ballot. People believe Buhari's promise of a clean break from the dirty politics of the past as well as his vows to revive the flagging economy and defeat the Islamist Boko Haram insurgency. They give Buhari a decisive victory.
But four years later, the results of Buhari's first term office are disappointing.
Multiple armed conflictsWhen elected in 2015, very few people doubted Buhari's ability to clamp down on the Boko Haram attacks in northeastern Nigeria – after all, he was a former military general. And he initially made significant gains. But recently, Boko Haram has ramped up its attacks against both the military and civilians and the situation has dramatically worsened.
An estimated 60,000 people have fled their homes in northeastern Borno State the past three months. Nearly all of the residents of the town of Rann have abandoned their homes and sought safety in Cameroon after a renewed Boko Haram attack on the border town in January.
Read more: Voting under the threat of Boko Haram
Still, the situation remains relatively calm in the Niger Delta, the storehouse of Nigeria's crude oil which makes up nearly 90 percent of the country's exports. But this is only because Buhari's government has resumed paying stipends to former militants to end attacks – it had previously put the payments on hold, citing corruption.
In contrast to the Niger Delta though, multiple new armed conflicts are springing up elsewhere. In the center of Nigeria, farmers and herders are clashing over land while Kaduna and Zamfara states are being hit by a wave of kidnappings and violence by armed bandits.
Why can't Nigeria's military, despite a budget of around 1.5 billion dollars, get a handle on such clashes and attacks? ? Buhari is the commander-in-chief. And why does it often escalate the violence instead of helping curtail it?
In October 2018, the Nigerian army fired on dozens of unarmed Shia Muslim protesters in Abuja. The army admitted to killing 45. According to a New York Times video, some of the dead protesters had bullet wounds in their back, an indication they were shot while fleeing.
The consequences? None. The military made its own investigation into the shooting, with no real results.
President Buhari's reaction? Nothing. He failed to condemn the killings, choosing instead to stay silent.
All in all, a normal scenario for Buhari's first term. He only reacts, when many lives are already unnecessarily lost.
Desolate economic situationBuhari has also failed to deliver on his second promise to tackle the country's economic woes. Unemployment has risen dramatically from 8.2 percent to 23.1 percent since he took office. In Lagos, Nigeria's economic hub, it's virtually impossible to find anyone who has a word of praise for Buhari's economic policies.
To be fair, Buhari did inherit a state treasury plundered by kleptocrats and an oil-dependent economy at a time when global prices of crude oil were plunging. His election pledge to diversity the economy and strengthen local production was a step in the right direction.
But his policies have failed to take. The import ban on tomato paste, for example, didn't result in a boom in local tomato production, but rather in a Nigerian tomato paste with hardly any tomatoes in it. Economists and business people look annoyed, or even shocked, when Buhari pats himself on the back yet again for his reforms.
Anti-corruption efforts working – albeit slowlyBuhari has seem some success on this third promise of tacking corruption. His intentions and actions are important and honest. But the system is so sick that progress is at a snail's pace. Critics say Buhari's desire to control everything himself is further hampering any headway.
And there's also the question of how much Buhari is physically capable of. The 76-year-old spent spent from May 2016 to mid-2017 in London for medical treatment. To date, he hasn't disclosed details of his condition.
Read more: Nigeria's president denies death rumor
The problem is that the issues facing Africa's most populous country can't wait. They keep getting bigger.
Disillusionment is rifeIn contrast to the adoring crowds of 2015, only around 5,000 supporters waited for Buhari's speech at his recent rally in Lagos, a city of 20 million people. During the three minutes he spoke, he called for voters to reelect him so that he could fulfill the 2015 campaign promises.
Although everything speaks for Buhari's blistering electoral defeat, it probably won't happen for two reasons. Firstly, he has overwhelming support of northern voters, who see him as a down-to-earth man of the people.
Secondly, the alternatives aren't much better. The People's Democratic Party is the strongest opposition party – that's the same party that failed to improve Nigeria during 16 years of rule from 1999 to 2015.
The PDP's presidential candidate is Atiku Abubakar, a former vice president and customs official. He started a logistics company while employed as a civil servant, rapidly amassing immense wealth, the source of which he has been unable to explain. While he has been the subject of corruption investigations in Nigeria (and elsewhere), Atiku has never been convicted.
Find out more about Atiku in this profile
He's hardly a plausible vision for the future of Nigeria.
Nevertheless, it will be a tight race between Buhari and Atiku.
"You have to chose the lesser evil," Nigerians keep telling me. But that's not quite true. There are nearly 70 other candidates running for president – among them bright minds who aren't part of the country's elite and who haven't been milking the country for decades.
It's these alternatives that deserve more attention – and the chance to rule the country.