Billionaire climate activist Tom Steyer said Tuesday that President Obama's yet-to-be-made decision on the proposed construction of the Keystone XL oil pipeline will not define his environmental and energy legacy, as he offered a robust defense of the president's record on those issues.

"It's unfair to say that any one decision defines it," Steyer said in an interview on C-SPAN's "Newsmakers" that will air Sunday. He praised the president and his team for prioritizing climate, energy and environmental matters. While Obama's decision will be very substantial, Steyer said, it's an overstatement to say it will overshadow everything else.

"He's going to have a body of work on energy and the environment that is not going to be totally dominated by Keystone," said Steyer, a staunch opponent of constructing the pipeline from Canada’s oil sands to the Texas Gulf Coast.

The Obama administration announced last week that it would delay its decision on Keystone, a move that likely pushes the issue back beyond the midterm elections. Steyer, who plans to spend big money in key races in 2014, said the move does not change his November outlook.

Steyer reportedly plans to spend as much as $100 million on 2014 races, split between personal money and contributions from donors. He raised the possibility of spending even more than that Tuesday.

"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 2013. Steyer spent $8 million helping Democrat Terry McAuliffe win the Virginia governor's race and also used his cash to help Democrat Ed Markey (Mass.) get elected to the U.S. Senate.

Steyer rejected the comparison some have made between him and the conservative billionaire Koch Brothers, whom Democrats have sought to turn into midterm bogeymen. He chuckled when asked whether there are similarities and argued that the Koch brothers are much more self-interested.

"Their policies line up perfectly with their pocketbooks, and that's not true for us," he said. "What we are doing is we are trying to stand up for ideas and principles that we think are incredibly important but have nothing to do with our incomes or assets."

Steyer, who founded a climate-oriented group called NextGen Climate, declined to offer new specifics about the races in which he plans to play. He said he anticipated getting involved in "eight or more" contests including two that have already been mentioned -- 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 map.

Elections featuring 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 Steyer plans to enter, he said.

How will Steyer judge whether his midterm foray is a success? Wins.

"I've spent my life up to 22 playing a lot of sports so I really care about wins," he said. "I don't think there's any way you look at elections and don't look at it in terms of wins and losses."