TIJUANA, Mexico (AP) _ There was a lot of pride in this Pacific coast state when voters in 1989 did something unheard of: they ousted Mexico's ruling party from Baja California in a victory for democracy.

At the time, many were incredulous that the Institutional Revolutionary Party, or PRI, had lost and even conceded its first gubernatorial defeat since 1929. The winner was the pro-business, conservative National Action Party.

But Baja California today confronts rising drug violence, corruption among police and government officials and old political suspicions reawakened by the slaying of Mexico's ruling party candidate for president.

The candidate, Luis Donaldo Colosio, was gunned down March 23 at a campaign rally in Tijuana, Baja California's bustling city of 1.5 million that is the busiest crossing along the 2,000-mile U.S.-Mexico border.

But the killing was just another case of rising violence. To many, Tijuana has become the ''Medellin of Mexico'' as well-armed cartels battle for exclusive rights to smuggle Colombian cocaine into the United States.

''Colosio's assassination is one of many that occur in Tijuana every day,'' said Tonatiuh Guillen, a political scientist with Colegio de la Frontera Norte, a Mexican think tank. ''People are afraid and concerned.''

Twenty days before Colosio's murder, a clash March 3 between state and federal police left three federal drug agents and a state police officer dead. Authorities suspect a fight among cops hired to protect rival traffickers.

On Wednesday, state attorney general Juan Francisco Rios was fired by Gov. Ernesto Ruffo after police credentials bearing his signature showed up in the hands of drug traffickers. Reportedly, police sell credentials for between $2,000 to $10,000.

Rios denied wrongdoing, saying it was forgery.

But such charges are commonplace. State government spokesman Gabriel Guzman said 150 police were fired for corruption last June alone. Investigations go on constantly, with limited effect.

''We inherited a primitive system, a structure with the old guard and we face a lot of resistance,'' said Guzman.

Drug trafficking and violence escalated after the 1989 arrest of powerful northern Mexico druglord Felix Gallardo, based in Sinaloa.

His cartel splintered into five groups distributing cocaine and marijuana along a Pacific corridor encompassing Sinaloa, Baja and several other states. Police say the power struggle escalated last year with bombings and executions.

Last May's killing of Roman Catholic Cardinal Juan Jesus Posadas at the Guadalajara airport was among the most notorious of the attacks.

Authorities have blamed Tijuana's Arellano Felix cartel for a botched hit by gunmen who apparently mistook the Roman Catholic cleric for rival trafficker Joaquin ''El Chapo'' Guzman.

''Many Baja Californians are asking, 'Why is this happening in Baja California?' '' said Ruffo, who has fought back with frequent police and bureacratic shakeups. ''Events like these don't help at all.''

Many believe it was no coincidence that Colosio was killed in Tijuana, although investigators so far have no evidence of conspiracy. They suspect someone might have wanted to shame Mexico's first opposition state government.

Roger Guevara, a U.S. Drug Enforcement Administration spokesman in Washington, dismissed speculation that traffickers killed Colosio, saying the last thing the cartels want is more attention.

Amid the upheaval, the opposition government continues to receive good marks from many.

People here boast of a more open administration, with close U.S. ties, and one that created the first voter registration card with a photograph, an idea intended to deter fraud that has since spread nationwide.

''There has been a radical change,'' said political scientist Guillen. ''The parties are more civilized, there is more tolerance and respect. And there are new, intense public debates, less bureaucracy.''

But Ruffo called the enduring drug violence and corruption ''the worst problem'' facing the Mexican government and one that goes far beyond his state.