Mitt Romney, the Republican presidential nominee in 2012, threw a little cold water Sunday on the brewing speculation that he will mount a third White House bid in 2016.

“I’m not running, I’m not planning on running,” Mr. Romney said in an interview on “Fox News Sunday,” in response to a question about his future ambitions.

Mr. Romney’s name continues to surface in speculation about which candidates will throw their hat in the ring in 2016 for the Republican presidential nomination. Some polls show him leading the potential field.