In politics, it rarely pays to be above the fray. So when a billionaire bent on making his mark comes to your movement with open wallet, you welcome him with open arms.

That's how Tom Steyer and the environmental community grew to be fast friends.

The former manager of a San Francisco hedge fund has pledged $50 million of his own money, and to raise a matching amount, for November's congressional and state elections through his NextGen Climate Action PAC to address what he calls "the generational challenge."

He is focusing on defeating Republicans, who largely deny or are skeptical of the scientific consensus that human activity -- mainly, burning fossil fuels -- is producing greenhouse gas emissions that drive climate change.

In spending so much money, he is making a name for himself as well as raising the political stakes.

"I think he's brought a political focus to the climate issue — he's politicized it, certainly. He's brought some political heat in. We've listened to scientists say for 30 years this is an issue and not seen much action out of Congress, sadly," said Jamie Henn, spokesman with climate advocacy group

Whereas former Vice President Al Gore has served as the omnipotent Cassandra-in-Chief for climate change who conservatives brushed off, Steyer brings a $100 million sledgehammer.

And that's the lowball figure.

"If you said to me, how much would I be willing to spend to make this, what I believe it really is, the most important issue in the minds of Americans, then I would think a hundred million bucks would be very low, honestly," Steyer, 56, said last month on C-SPAN's "Newsmakers."

Steyer's rising prominence comes as the Obama administration is gearing up for a renewed climate push, just weeks after it punted again on the Keystone XL oil pipeline. The White House on Tuesday released its third National Climate Assessment, which said global temperatures were expected to rise another 3 to 5 degrees Fahrenheit by the end of the century, even in a low-emissions scenario.

Environmentalists have struggled to compete financially with multibillion-dollar oil companies, which donate overwhelmingly to Republicans. Instead of legal tender, the movement has used morality — the stewardship of Earth, leaving the world in a better place for the children, post-industrial nations taking responsibility for greenhouse gas emissions — as its currency.

The fossil fuel industry likely will still outspend environmental groups. Steyer's involvement evens things out a little.

"At the end of the day, the fossil fuel industry no longer has the playing field to themselves," League of Conservation Voters spokesman Jeff Gohringer told the Washington Examiner. "We need more environmental money in politics."

Steyer's emergence has emboldened congressional Democrats to speak out on climate change, an issue that was a no-go following the 2010 collapse of cap-and-trade legislation. In March, for example, 30 Senate Democrats held the floor overnight to talk about climate change.

To the political Left, Steyer is seen as a counterweight to Charles and David Koch, who made their fortune in fossil fuels and whose contributions to conservative lawmakers have helped create gridlock on climate legislation. Democrats have increasingly railed against the billionaire brothers in the run-up to the midterms, just as Steyer's profile has been soaring.

Steyer and his environmental supporters dismiss those who say he is the Democrats' version of the Kochs.

"I think there are real distinctions between the Koch brothers and us. I think one thing is their policies line up perfectly with their pocketbooks, and that's not true for us," Steyer said of NextGen Climate on "Newsmakers." Steyer, through NextGen, declined an interview request.

That said, as an investor in clean-energy technology, Steyer stands to benefit from some of the climate policies the Obama administration is advancing -- chiefly, limits on carbon pollution from new and existing power plants, which form the cornerstone of President Obama's climate agenda.

Steyer's actions on climate could also benefit him politically. His name was bandied about as a possible energy secretary pick before Obama chose Ernest Moniz last year, and he's left the door open to political opportunities.

"What I have said is I would do anything, really, that was sensible and legal to push the United States in the right way on this issue. And if that meant running for office, then I'd do it," Steyer said on C-SPAN.

He's got the credentials and the looks for it.

A shock of light-brown hair and a strong jaw, square chin and well-defined cheekbones have served him well for the many TV appearances he's made in recent months. He and his wife, Kat Taylor, run a small bank that focuses on environmental and social-justice clients who have trouble securing loans from other institutions. They have four grown children.

He also has amassed a net worth estimated at $1.6 billion.

New York City-raised, he was top of his class at the prestigious Phillips Exeter Academy boarding school before graduating summa cum laude and captaining the soccer team at Yale University in 1979. He went back to New York to work at Morgan Stanley, then got an MBA in 1983 from Stanford University before heading back to the Big Apple to work at Goldman Sachs.

His interest in climate change started with a June 2012 Rolling Stone story by founder Bill McKibben. The story, "Global warming's terrifying new math," said that 80 percent of the world's oil, coal and gas reserves would need to stay in the ground to avoid irreversible, catastrophic effects of climate change.

At the end of 2012, when he left Farallon Capital Management, the San Francisco hedge fund he started in 1986 after leaving Goldman Sachs, he told investors he needed to work on climate advocacy full time. When he learned that some of his investments were tied up in pipeline companies that deal in oil sands and coal, he divested.

"I came to realize that I could no longer in good conscience remain in a business that by definition was invested in every sector of the economy, including the energy sector, while knowing the detrimental impact of fossil fuels on the health, safety and security of our children," Steyer, on NextGen Climate's website, wrote of his decision to leave Farallon.

NextGen Climate already has run advertisements bashing Sen. Marco Rubio, R-Fla., who isn't up for re-election until 2016 but whose state is confronting rising sea levels and has a gubernatorial election this year. The group is backing Rep. Bruce Braley, D-Iowa, in the contest to fill retiring Democratic Sen. Tom Harkin's seat. NextGen Climate will firm up its other plans around June, Steyer has said.

The Right has accused Steyer of meddling in political affairs and of being too cozy with the White House, citing Steyer's political connections, such as his friendship with Obama adviser John Podesta.

"All the money Tom Steyer has spent over the past year has had almost no impact, or little impact, other than in the White House — which, of course, is the key one," Matt Dempsey, a spokesman for industry group Oil Sands Fact Check, told the Examiner.

Nowhere was that more apparent, Republicans say, than with last month's delay of the $5.4 billion Keystone XL pipeline.

The State Department said it would halt its review of the Canada-to-Texas project while it waits for the Nebraska Supreme Court to rule on the legality of the pipeline route. That likely will put a decision on the pipeline, which has been under federal review more than five years, beyond the November midterm elections.

Conservatives said the move was a sop to Steyer. They accused Obama of avoiding making a decision that would anger his environmental base before the midterms or jeopardize a clutch of pro-Keystone Democrats running tight Senate re-election contests in red-leaning states.

But the man who made his name nationally on Keystone has softened his tone in recent weeks. On "Newsmakers," Steyer said it would be an "overstatement" to say approving the pipeline would undermine Obama's climate legacy.

He also has backed off targeting candidates just for their Keystone leanings. Now he says he will invest in races where there's a significant difference between candidates on environmental issues and where substantive change was possible.

For Henn, that's fine. His group will hold the line on Keystone, and Steyer — and his money — can focus on maintaining the Senate for environmentally friendly Democrats.

"This is a political issue, and I think it needs to be seen as that. There really are big money interests at stake, and we're not going to have any movement on climate unless we take on the fossil fuel industry," Henn said. "We felt we needed to get more political instead of wandering around on the sidelines making moral statements."