* Smooth transition of power hailed after president dies
* Vice president takes over until vote
* Uncertainty over party contenders could hit currency (Adds quotes from former president Rawlings)
By Kwasi Kpodo
ACCRA, July 25 (Reuters) - Ghana has seen a smooth transition of power after the sudden death of its president, but as the nation mourns attention is already turning to who will replace him as the ruling party's candidate in a December vote.
Vice-President John Dramani Mahama was sworn in hours after the announcement of the death through sudden illness on Tuesday of 68-year-old President John Atta Mills.
This ensured that the West African oil, gold and cocoa producer, a former British colony once known as the Gold Coast, avoided the kind of messy political transitions that have plagued other states in a coup-prone region.
Ghanaians congratulated themselves on the seamless handover. Mahama, 53, a historian, former minister and communications expert, is expected to bring a steady hand to a fast-growing economy, one of Africa's newest oil producers.
But questions over who will now step into Mills' shoes as the candidate to keep his governing National Democratic Congress (NDC) in power in December's elections will inject some uncertainty into the political outlook.
Analysts say this could drive down the Ghanaian currency, which has lost about 17 percent against the dollar this year as the country's oil-fuelled boom sucks in capital and consumer imports and drives up demand for dollars to pay for them.
Traders said the cedi was relatively stable on Wednesday at 1.9550/1.9600 to the dollar.
"Political disruption is likely to be internal and will focus on who is the NDC's presidential nominee," said Azim Datardina, Ghana analyst at Africa Risk Consulting.
Mills, seeking a second term despite having suffered for years from undisclosed health problems, had already won his party's nomination to run against the opposition New Patriotic Party's Nana Akufo-Addo, defeating a divisive challenge from the wife of still influential former president Jerry Rawlings.
"This was certainly the wrong time for him to go considering that we have elections right around the corner," Rawlings told the BBC on Wednesday.
"Quite frankly, had he been advised and done something wiser earlier, I think he could have survived for another six or seven months," he said.
Some analysts expect Nana Konadu, Rawlings' wife whom Mills crushed in the NDC primaries, to claim an automatic nomination.
But Alban Bagbin, Ghana's health minister and a member of the NDC legal team, said the party would hold an extraordinary meeting to pick a new candidate for what is expected to be a tight race for the presidency.
"Most likely is a new nomination contest with a number of high-profile challengers who earlier balked at opposing Mills. A likely candidate is John Mahama," said Africa Risk Consulting's Datardina.
Flags flew at half mast on Wednesday as the nation began a week of national mourning for Mills, who had served as president since winning a 2008 presidential contest that won plaudits for going down to the wire but remaining peaceful.
"I am personally devastated - I've lost a father, I've lost a friend, I've lost a mentor and a senior comrade," Mahama said in his first comments after being sworn in before a sombre parliament on Tuesday evening.
"The fine gentleman that he was, President Mills rightly earned the title 'Asomdwehene' (King of Peace). He brought a distinctive insight to Ghanaian politics. He remained humble, honest and modest throughout his years in public service."
That sense of loss was shared by ordinary Ghanaians too.
"I didn't know him personally but he's everybody's father and a peacemaker," said Peter Fiave, a 70-year-old who went to parliament to witness the swearing-in of Mahama.
Tributes poured in from around the globe from heads of state including U.S. President Barack Obama, who had feted Ghana under Mills as a model and "good news story" for Africa.
Rivals were quick to praise the nation's handling of the sudden loss. "We are showing a maturity that must encourage all Ghanaians," said opposition NPP Chairman Jake Obetsebi-Lamptey.
Mahama, fresh from a U.S. tour to promote a recently published personal memoir on Ghana's history, is widely expected to maintain current policies in his caretaker role.
Yet, amid the plaudits for his predecessor, he will inherit the same struggles Mills had faced in managing Ghanaians' high expectations over the flow of crude from the country's Jubilee oil field since 2010, and in tackling corruption scandals that have dogged the NDC administration.
"Given the above, recent momentum has favoured the NPP. Ghanaians also have a history of evicting the ruling party at the ballot box in favour of the opposition," Standard Bank said in a research note on Wednesday.
"Much will hinge on the manner in which the NDC is able to swiftly elect a replacement presidential candidate. Infighting already poses a significant threat to party unity, and any signs of an exacerbation of these tensions will favour the opposition," it said.
Former president Rawlings offered a glimpse of the kind of bad blood that exists within the party when he appeared to criticise Mills' achievements in office in the BBC interview.
"Considering that the cancer affected both his eye and his ear, he couldn't sustain more than three hours per day. So it was naturally going to affect his performance," Rawlings said.
Ahead of Mills' death, most analysts had expected a year of election spending testing Ghana's reputation for improved economic management. The government last week sought parliament's permission for extra spending.
"We think heightened uncertainty will result in some foreign investors taking a wait-and-see stance, which would imply a slowdown in FX inflows, which in turn would be negative for the already troubled cedi," Renaissance Capital said.
"We think another 5-10 percent depreciation is likely by (the end of 2012)," it said. (Additional reporting by Ed Cropley in Johannesburg and Joe Bavier in Abidjan; Writing by David Lewis; Editing by Pascal Fletcher)