SACRAMENTO—Peter Miguel Camejo, a three-time Green Party candidate for governor and Ralph Nader’s 2004 vice presidential running mate, died early Saturday at his home, family associates said.

Camejo’s wife, Morella, was with her husband when he died of lymphoma, just days after finishing an autobiography, consumer advocate Nader said in a written tribute.

Camejo, 68, was a longtime Folsom, Calif., resident and a fierce advocate for third-party political activism, in California and nationally. He also was a pioneer in the movement to create investment funds stressing environmental conservation and fair treatment of workers and communities.

Recently he was treated at UC Davis Medical Center for the cancer, which had recurred, according to a statement by his family.

Camejo was born Dec. 31, 1939, in Queens, N.Y. He was the son of an affluent Venezuelan couple, and he grew up in Caracas and New York City before settling with his mother on Long Island.

After earning a perfect score on the math section of the SAT college entrance exam, Camejo enrolled at the Massachusetts Institute of Technology, but dropped out to become a civil rights activist in the South.

He later returned to college at the University of California, Berkeley. He joined the anti-Vietnam War movement and was expelled for his role in campus protests.

In 1976, he embarked on the path that led to a reputation as a political maverick—a run for president, representing the Socialist Workers Party.

As the Green Party’s candidate for governor of California in 2002, he garnered 5.3 percent of the vote, Nader said.

In the 2003 recall election of then-Gov. Gray Davis, Camejo debated Arnold Schwarzenegger and Davis and eventually won 3 percent of the vote. He ran again in 2006, but said it was his last campaign.

“Peter was a friend, colleague and politically courageous champion of the downtrodden and mistreated of the entire Western hemisphere,” Nader said in his e-mail. “Everyone who met Peter, talked with Peter, worked with Peter, or argued with Peter will miss the passing of a great American.”

Camejo also became an adviser to investment funds with a social and environmental bent.

Among his achievements was the creation of the Eco-Logical Trust for Merrill Lynch, the first fund of a major firm to hold investments to environmental standards.