In a front-page cartoon showing a ballot box full of votes locked away for safe-keeping while a group of citizens look on, Kinshasa daily Le Potentiel catches the mood of post-election Congo.

Dear Ballot Box, I hope you will tell me a story with a happy ending on December 6. It is the one I wrote, reads a speech bubble from one onlooker of the date when provisional results are due.

Despite chaotic preparations and outbreaks of violence, millions of Congolese patiently lined up to vote in their country's second post-war election on Monday, the first one to be locally managed after a U.N.-steered 2006 poll.

It is a potentially proud moment for the nation -- at last a chance to show the world that the former Belgian colony has what it takes to start shaping its own destiny.

But as results are ferried from remote polling stations to be tallied and sent to the capital, disorder during counting, rival claims of victory and text messages with unofficial results are creating a combustible mix.

Reuters journalists saw several examples of voters taking the law into their own hands, in one case nearly lynching an official accused of trying to stuff a ballot box.

At another, police were prevented from moving voter slips from one polling station to another which had run out, as voters feared they would be used fraudulently.

The frontline protection against fraud attempts during overnight counts in churches and classrooms across the country are poorly paid election officials, party representatives there to monitor the process -- and the Congolese themselves.

Asked if the result would be credible, Muila Kayembe of the Congolese RENOSEC election observer mission said: We hope so -- as long as the population stays vigilant.

Incumbent President Joseph Kabila, whose support base is largely in the Swahili-speaking east of the country, and veteran opposition leader Etienne Tshisekedi, popular in the teeming capital and southern Kasai regions, are frontrunners.

BREAK WITH THE PAST?

The candidates are preparing their positions ahead of the result declaration.

Tshisekedi's camp has said people would take matters into their own hands if the process is dishonest while Kabila's government has said he would accept defeat but the security forces would stop attempts to challenge results on the streets.

While former parliament speaker Vital Kamerhe has said he will accept the results, three other opposition candidates have called for them to be annulled. Whoever is declared winner, a dispute of some kind is almost guaranteed.

Kabila can expect to do well in southern Katanga province and in the east, although analysts have said his strong support in the last elections may be diminished due to continued insecurity and poverty.

A potential flashpoint is Kinshasa, the nation's capital and a crumbling home to some 10 million people who have seen scant improvements in their lives despite promises made by Kabila after his 2006 election win.

Among Tshisekedi's supporters, there is an almost religious belief that their candidate -- despite his 76 years and brief stint as prime minister for ex-dictator Mobutu Sese Seko -- can mark a genuine break with the past.

After decades in opposition and having boycotted the 2006 poll in which Kabila defeated businessman and ex-rebel leader Jean-Pierre Bemba, the veteran Tshisekedi is seen neither tarnished by the war nor by Congo's murky peacetime politics.

Ironically for someone who has spent years abroad, partly to seek medical treatment, Tshisekedi has nurtured a one of us image that resonates with many Congolese fed up with years of foreign interference -- first in the Cold War and then during two regional wars that sucked in the armies of Congo's neighbours.

Results posted at dozens of polling stations in Kinshasa visited by Reuters journalists this week confirmed Tshisekedi's popularity. When he was prevented from campaigning last weekend, tens of thousands of people took to the streets of poor neighbourhoods.

I have gone everywhere and it is only Tshisekedi who is winning, said civil servant Richard Kadima, a father of two.

I don't know what magic Mulunda will use to get his candidate elected, he added, repeating allegations that the head of the election commission, Daniel Mulunda Ngoy, is pro-Kabila.

Mulunda denies such accusations. Kabila's camp has described the unofficial vote tallies showing a Tshisekedi lead as fantastical.

Chaotic scenes at least one of the compilation centres in Kinshasa, where bags of votes were being dumped on the ground outside a warehouse, has done little to inspire confidence in the process so far.

Tshisekedi's homelands in the southern Kasai provinces saw some of the worst violence during voting, with dozens of polling stations torched in frustrations over delays, prompting fears of trouble there should Kabila be declared winner.

Both the United Nations and the European Union have appealed for calm, while Congo's media watchdog threatened sanctions against anyone printing information that triggered violence.

Fearing trouble, many expatriates have left the country.

(Writing by David Lewis; Editing by Rosalind Russell)