For the first time in Mexican history, an opposition party finds itself defending a state governorship.
By coincidence, the state in question also happens to be the home state of Mexico's president - Baja California.Sunday's election is more a test of the strength of the conservative National Action Party, known as the PAN, than of its candidate Hector Teran Teran.
The 1989 gubernatorial victory of Ernesto Ruffo Appel was the first ever by an opposition candidate since President Ernesto Zedillo's Institutional Revolutionary Party, or PRI, was founded in 1928. Never before had the PRI conceded such a loss, often staying in power by fraud or intimidation.
Since 1989, the PAN has won three other governorships, two of them this year. A loss by Teran would hurt its momentum and boost the PRI, which has hit by economic crisis and political reforms loosening its grip on power.
"Baja California is an example for Mexico to follow," said political scientist Leo Zuckerman. He noted that voters here have traditionally been more nonpartisan and independent than elsewhere in Mexico.
Recent polls give as much as a 10 percent lead to Teran, except possibly in the state capital Mexicali. Its mayor, Francisco Perez Tejada, is the PRI's candidate.
Gov. Ruffo has been given high marks as an administrator, and the PAN has touted Ruffo's rule rather than Teran's attributes as a reason for keeping the party in power. "He didn't enrich himself, he wasn't corrupt, he didn't buy journalists," posters in Mexicali boast - of Ruffo, not Teran.
The hardest moment of Ruffo's term came on March 23, 1994, when PRI presidential candidate Luis Donaldo Colosio was killed during a campaign rally in Tijuana - an assassination that shook Mexico and remains unsolved.
In addition, many in Ruffo's administration were fired for corruption and links with drug traffickers. His brother was investigated for ties with cocaine barons, although no proof was found.
In his campaign, Perez Tejada has used Colosio's murder and drug-related violence as examples of the lack of security under the PAN.
Grocery clerk Armando Reyes, 30, disagreed. He said people "don't believe Colosio's murder affects the PAN because it didn't have anything to do with it."