Honolulu mayoral candidate Ben Cayetano says he will sue the pro-rail Pacific Resource Partnership for defamation.
Cayetano has hired a local law firm with his own money and plans to file the lawsuit as early as next week.
He said PRP is spending as much as $2 million dollars in attack ads, knowing they are false.
"That's the frustrating part of it," Cayetano said. "They know it's not true and yet they continue to do it because they want to win this election and make sure I don't do it."
Cayetano, who opposes rail, says the lawsuit aims to clear his record and find out who's financing PRP's ads.
Most of PRP's money comes from the local Carpenter's Union ... but PRP is not required to disclose its other donors.
"I think they have a lot of things to hide themselves," Cayetano said.