A prominent U.S. law firm accused Chevron Corp of mounting a "smear campaign" aimed at keeping it out of a high stakes Ecuadorean environmental pollution case. The accusation, contained in court documents filed…by Patton Boggs of Washington, D.C., comes a day before a hearing on a new civil racketeering lawsuit by Chevron against Ecuadorean plaintiffs…The Ecuadorean plaintiffs started their litigation in 1993 against Texaco -- bought by Chevron in 2001. They accuse it of dumping oil-drilling waste in unlined pits, contaminating the forest and causing illnesses and deaths among local people…In the court filings…, Patton Boggs asked a federal judge…to allow it to bring tortious interference claims against Chevron and its outside counsel, Gibson Dunn & Crutcher…Gibson Dunn partner Theodore Boutrous Jr. called the Patton Boggs filing "frivolous and incoherent"…