Lagos - When Kofi Annan, the former UN secretary general, was in Abuja last week, he urged all presidential candidates and parties to rise above the personal and debate the issues that matter.But the message appears to have gone unheeded, with fresh attacks from the ruling Peoples Democratic Party (PDP) against Muhammadu Buhari, from the main opposition All Progressives Congress (APC).Buhari, who hails from the Muslim-majority north, has previously been accused of being an Islamic extremist, of failing to finish high school and alleged monumental fraud.On Sunday, President Goodluck Jonathan's campaign chief Femi Fani-Kayode added another claim, publicly mentioning "rumours" that the 72-year-old was "mortally ill" from prostate cancer."We are therefore constrained to urge him to prove to the Nigerian people that he really is as 'fit as a fiddle'... by taking a brisk walk or even jogging around the perimeter of the stadium before any of his rallies," he said in a statement."If he can do that, it will go a long way to allay the fears of many."Raising fears about the health of a man who could become president recalls the presidency of Umaru Yar'Adua, who died in office in 2010 from a kidney related ailment.He was believed to have had health issues even before he assumed office in 2007 but were never disclosed.Buhari, a former military ruler, said the claim smacked of desperation on the part of the ruling party, with the 14 February vote widely predicted to go down to the wire."How they got the impression that I was sick I don't know," he told a news conference on Sunday, revealing that the only health issue he had was a cold.Instead, he said the medical document said to back up the PDP claims was forged and was designed to avoid the main issues in the election, including widespread corruption at the highest level.Gutter campaignBuhari has come under personal attack in part because of his time in the military, which saw him seize power from a democratically elected government in a coup in December 1983.For the PDP, a leopard can't change his spots and the party has been whipping up the politics of fear, harking back to the days of the former army general's crackdown on corruption and indiscipline."No matter how many pretty robes you wear, once a tyrant, always a tyrant," one PDP newspaper advertisement ran on Monday, over photos of Buhari in uniform, a dinner jacket and ethnic attire.Others evoked the jailing of political opponents or his muzzling of the media during his 20 months in power.Whether the tactic pays off for the PDP will only be seen when the results come in, with no independent polling currently available to assess voting intentions.But for politics watchers, the standard of the campaign is a worrying development, arguing that it does little to help enhance already shaky confidence in the country's leaders.Fell into trap"I think it has a negative impact on the political process and citizens aren't able to see the quality of people running for election," said Clement Nwankwo, director of the Policy and Legal Advisory Centre, a pro-democracy group."What they see is personal attacks, falsehoods, concocted stories and political smearing... that has not elevated the debate," he told AFP.For Nwankwo, the APC has fallen into a PDP trap by responding to the claims instead of rebutting the allegations by continually questioning the government's achievements.Dapo Thomas, a politics lecturer at the Lagos State University, called it a "gutter campaign" borne out fear in the PDP that it could lose power for the first time in 16 years.The electorate may be able to see through it, he suggested, particularly as some of the issues had not been raised on the three previous occasions that Buhari stood for the presidency."They [the PDP] have seen the writing on the wall," he added.