Markey Asks Calif. Billionaire to Butt Out of Mass. Senate Race

His opponent targeted over Keystone XL

U.S. Rep. Edward Markey is asking a California billionaire to stay out of the U.S. Senate race in Massachusetts.

Markey said in a statement Friday that Thomas Steyer should immediately withdraw his threat to unleash negative attacks against Markey's Democratic rival, U.S. Rep. Stephen Lynch, unless Lynch denounces the Keystone XL Pipeline by "high noon."

Steyer and other critics of the proposed pipeline from western Canada to Texas say it will carry "dirty oil" that contributes to global warning. Lynch supports the project, while Markey opposes it.