This town on the banks of a vast tropical swamp lost its mind one day this month.

In an act of collective rage following the assassination of a beloved mayoral candidate, roughly 500 men and women ransacked government offices, the headquarters of rival politicians and the state-run phone company. The mob used sledgehammers to weaken walls, gasoline to burn filing cabinets and furniture inside, and stones to batter away at the bricks. Much of the work, carried out through the night of Nov. 7, was done with bare hands.

The spontaneous uprising marked a new turn in Colombia's year-long experiment with civil resistance as a way of opposing the various armed groups engaged in its long civil war. It came as the new U.S.-backed president, Alvaro Uribe, urges citizens to stand up to the two leftist guerrilla groups and a privately funded paramilitary force that are dominant in much of rural Colombia.

Uribe's idea has been to seek ordinary people's help in the effort to strengthen the state's security presence -- the army and police instead of irregular combatants from the left and the right -- in the loosely governed countryside. The vacuum in government authority has been cited as one of the main reasons the war, in which the Bush administration has made a growing commitment on the side of the government, seems to endure year after year with no end in sight.

Even before Uribe took office in August, civil resistance to armed groups was blooming in Colombia's countryside. Early this year, a series of village demonstrations began against the Revolutionary Armed Forces of Colombia, or FARC, as the largest leftist insurgency is known. With the small revolt here in Concordia, the protests have now extended to violent resistance against the United Self-Defense Forces of Colombia, or AUC, a paramilitary force that combats the guerrillas, often in tandem with the official army.

The townspeople who went on a rampage here hold the AUC responsible for killing Eugenio Escalante, 47, a favorite son whose body turned up soon after he met with several paramilitary leaders who wanted him to get out of next month's mayoral elections. The AUC has deep ties to Colombia's political and financial establishment. The links are strong here, too, and Escalante apparently was killed for campaigning on a promise to end them.

For at least two years, townspeople said, the sitting mayor and his allies have given the paramilitary group a slice of the municipal budget. In addition, they said, the municipal authorities have looked the other way while the AUC carried out a brutal "cleansing" campaign against drug users, drunks and presumed leftists. Finally, the disgruntled town residents charged, the local authorities plotted with AUC leaders to stay in power -- making Escalante's popular candidacy a threat.

Only those buildings associated with the current municipal government were sacked, leaving intact the small pink hospital and the school that were financed by the central government. The entire municipal government has since fled. Local paramilitary leaders have also stayed away.

"This was indignation," said a doctor here, bleary from drink, sleeplessness and fright, who like all those interviewed during a recent visit declined to be identified for fear of reprisal. "No one that night was acting with a clear head. This was a murder that was planned, and now it is going to be very difficult for this group to operate here with any help from us."

A native son who earned his medical degree in Paraguay, Escalante was ultimately too brave or foolhardy to survive politics in this town, which lies 390 miles north of the capital, Bogota. It has never had a permanent National Police presence or an army base. Instead, guerrilla and paramilitary forces have taken turns standing in, leaving local officials to the whims of whichever of the armed groups was in ascendancy at the time.

More than half of Colombia's 1,098 mayors are working under death threats issued by guerrilla or paramilitary groups, according to the Colombian Federation of Municipalities. Over the course of this year, 10 mayors have been killed and 10 others kidnapped. Their fate underscores the importance that the armed groups place on controlling the budgets and political agendas of local governments.

Concordia's early mayoral race, only the second here since it became an independent jurisdiction in the year 2000, offers a grim preview of the hundreds of regularly scheduled municipal elections next year. Gilberto Toro, director of the municipal federation, said "the situation would be pretty much the same for candidates almost everywhere" if the elections were held now. In 2000, 18 mayoral candidates were killed across the country.

"In some cases, candidates were forced to make alliances with the armed groups," Toro said. "At times, the people have managed to protect their leaders, mainly by surrounding them or protesting vigorously against the threats, but this time they couldn't. Despair led them to react the way they did."

Concordia sits on a low sweep of land that juts into a broad swamp dotted with clumps of water lilies. Twin yellow church bell towers, draped with Spanish moss, rise from the banks. On the choppy water, fishermen stand in shallow canoes casting nets, as hundreds of white herons swarm above for a chance to scavenge the catch.

Many of Concordia's sagging plaster and mud houses date to the turn of the century. The muddy streets have never had a patch of pavement. Pigs root in tall grass while peacocks bounce among the tin rooftops, a rare graceful note in an otherwise bleak village landscape.

From many of the town's walls, Escalante's bespectacled gaze still glowers from campaign posters under a crown of black hair parted in the middle. A dermatologist by training, he was a father of three young children and brother of 10 siblings, so many here are related to him by blood. "Special," "smart" and "determined to change this place" were the most frequent descriptions of him, offered by people too frightened to say more than a few anonymous words.

Escalante's slogan, "Welfare and Progress," still splashes across the wall of a small home at a split in the dirt road entering town. A statue of the Virgin Mary sits at the divide, across from the headquarters of Anibal Castro, handpicked by the current mayor and his paramilitary patrons to succeed him. Castro, also a doctor, has since fled town. Only his torched office remains, its tin roof collapsed on a pile of ashes.

His political sponsor, sitting Mayor Pablo Salas, fled to the provincial capital of Santa Marta as the mob gathered force and reduced City Hall, the Municipal Council building, the Social Solidarity Network headquarters and the Telecom office largely to rubble and ash. Salas, according to townspeople, essentially answered in his daily duties to a woman named Sonia. She was identified by residents as the local commander of the AUC's Northern Bloc, which arrived two years ago to evict the FARC from this town and others like it along the Caribbean coast.

The fight here has been mainly for strategic position. Concordia sits near the Rio Magdalena, Colombia's largest river, which is used like a highway to move drugs, guns and goods from the interior to the coast. Neither group has offered much of a political program for the town over the years, viewing it as a place to raise money and hold ground against the other side.

In the weeks before Escalante's murder, Sonia asked him several times to leave the race as it became clear that he would win and end the paramilitary's cut of the budget.

"Look around this town, take pictures of it, and you will see not one bit of government action on our behalf," said a longtime resident, adding that much of the public money went into paramilitary pockets. "He [Escalante] told me late last month that he was being pressured to pull out. He just said, 'I'll never do it.' "

On the afternoon of Nov. 7, Escalante was summoned to a meeting of paramilitary commanders, local ranchers and business leaders in a private home here, according to townspeople. Again he was told to leave the race to Castro, and again he refused. Two hours later, less than a mile on the main road out of town, Escalante's body was found at twilight. He had been shot four times in the head.

"The town erupted," said an old man with a red baseball cap sitting across from the ruined City Hall. "There is no democracy here, no government, just a caudilla who ordered this killing. Now, maybe, there is no one at all."

Escalante was buried a few days later at a funeral attended by 5,000 people, but his small yellow house across from City Hall is still the site of mourning. Dozens of his relatives -- brothers and sisters, their children, his wife -- line the walls of the dark living room in plastic chairs. Candles burn along one wall before a framed photograph of him and a cluster of flowers.

The town is terrified, awaiting the paramilitary response. But already, from the groups of men talking in whispers on many street corners, a plan has emerged to make their message clear in the mayoral election still scheduled for Dec. 15: "We're all going to vote for Escalante in his tomb," the doctor said.