Billionaire climate activist Tom Steyer plans to spend big money making an impact in the 2014 midterm elections. Like $100 million big, according to a report. But in an interview Tuesday, Steyer suggested that elevating the most crucial climate and environmental issues of the day in the eyes of the public might require even more money.

"If you said to me, how much would I be willing to spend, to make this what I believe it is, the most important issue in the minds of Americans, then I would think 100 million bucks would be very low, honestly," he said in an interview on C-SPAN's "Newsmakers" that will air Sunday.

The New York Times reported in February that Steyer plans to spend as much as $100 million on 2014 races, split evenly between a $50 million personal donation and $50 million in contributions from major donors. When pressed on a specific dollar figure Tuesday, Steyer refused to commit to one.

"Trying to say what you're going to spend or how it's going to play out is pretty unrealistic," he said.

Steyer's not yet telegraphing the list of races in which he plans to get involved. He said he anticipated getting involved in "eight or more" contests including the Florida governor's race and the Iowa Senate contest. Steyer anticipated firming up his plans around June, once the candidate fields come into clearer view across the country.

Elections that feature a "significant difference" between the candidates on energy and climate issues, "something important" at stake and the potential to make a "longer term impact" are the ones in which Steyer plans to spend, he said.

How will he judge the success (or failure) of his spending? It's all about the W's.

"You've got to realize how deeply superficial I am," Steyer said. "I spent my life up to 22 playing a lot of sports so I really care about wins. I don't think there's any way you look at elections and don't look at it in terms of wins and losses. We really like W's."