In what has become an annual rite, Chevron Corp.’s opponents in a South American environmental and legal quagmire have come to the United States in an effort to sway consumers, investors and politicians to support their cause.

The latest public relations campaign culminated during the San Ramon, Calif.-based company’s shareholders’ meeting Wednesday when a delegation from Ecuadorean rain forests contaminated by decades of oil drilling confronted Chevron Chairman David O’Reilly.