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(CNN) – Tom Steyer is a hedge fund billionaire bursting onto the political scene on behalf of environmental causes.
"There is a guy right here whose name is Tom Steyer. S-T-E-Y-E-R," said Sen. Jim Inhoke, R-Oklahoma, brandishing a Politico article at a recent Senate hearing on environmental protection. "He is a multi-billionaire. He is going to put $100 million into the legislative process to try to resurrect global warming as an issue."
"I don't know Tom Steyer from a bar of soap," said Sen. Jon Tester, D-Montana, at the same hearing.
Steyer is focusing on at least seven states that could decide which party controls the Senate, and key statehouses after November.
"We need to hold these politicians accountable. If they can't admit that climate change is real - we can't trust them," Steyer says in an ad for his political committee, NextGen Climate Action.
Last year, Ken Cuccinelli, Virginia's Republican candidate for governor, was defeated in a very close race. Steyer spent nearly $8 million helping him lose.
"We should all be proud of the work we've done to keep climate change denier Ken Cuccinelli out of the governor's mansion," Steyer says in a NextGen ad.
Steyer is also funding efforts to derail the controversial Keystone Pipeline.
All of which has Republicans crying hypocrisy, noting that Democrats have practically put the Republican-aiding billionaire Koch brothers on the ballot, decrying the brothers' influence on elections, while remaining silent about their own big-money donors.
Groups advocating campaign finance reform agree.
"Our democracy is not supposed to be the sport of kings, or a game for millionaires and billionaires on either side of the aisle to spend as much money as the want on politics buying government decisions, and buying access and influence," said Stephen Spaulding, with Common Cause.
"The United States Supreme Court has radically changed how campaigns work by allowing all this outside money to come in. I mean Tom would be the first to say ... that the laws that the Supreme Court have said and articulated, are not good for our democracy," said Steyer's adviser, Chris Lehane.
"But it's the reality that we're in," Lehane said. "The other option is to at least have someone out there who is trying to balance that playing field, to provide some resources for the other side."
Another point of contention involves Steyer's assets.
Steyer made his money as the manager of a $20 billion hedge fund, amassing a fortune through a variety of investments, including some in the very fossil fuels he now decries.
"He made most of his fortune in foreign coal investments, one of the energy sources he now says he wants to get rid of," said Tim Phillips, president of Americans for Prosperity, the conservative non-profit political advocacy group.
"I think a lot of Americans will see it has hypocrisy, and as political opportunism for Mr. Steyer," said Phillips.
But Steyer says it was those investments that led him to his most recent cause.
"I had to square myself ... with what I was doing in my own life," Steyer said in a speech at NextGen.
"Not only did he recognize it was not right, he decided to step down from the business that he had helped create, a fund that he was doing exceptionally well in, and decided to leave, and dedicate and donate the money that he has made to really fighting this," says Lehane.
Though Steyer divested from some of what he calls the dirtier fuels – coal and tar sands – his portfolio is, as of today, still not free of these investments. He has continued to make money off these unclean energies, while decrying them, and working to defeat politicians he sees as insufficiently committed to the cause.
Steyer has thrown lavish fundraisers for President Barack Obama, Vice President Joe Biden, Senate Majority Leader Harry Reid, and House Minority Leader Nancy Pelosi. He also spoke at the 2012 Democratic National Convention.
"Let's embrace a vision of a clean healthy planet, and not a scorched earth that can't sustain a future generation," Steyer told the 2012 DNC crowd.
"By the end of this month he will have become fully divested from fossil fuel companies," says Lehane. "People who know economics, know finance, know what divestment means, would understand and recognize that that meant an awful lot of money was left on the table."
Steyer's admirers argue that this is a guy who is fighting for the environment at his own expense, both because of investments he gave up or is about to give up, and campaign cash he's willing to spend.
With Steyer's $100 million on the table this election cycle, Senate Democrats – perhaps eager to have their names in his checkbook ledger – held an all-night session earlier this year to highlight his pet issue. Republicans were not pleased.
"Senate Democrats are just trying to please the left coast billionaire who will fund their campaigns," said Senate Minority Leader Mitch McConnell. "They introduced no new legislation."
Cynicism and criticism notwithstanding, Steyer sees combating climate change as good policy and good politics.
"At the end of the day you judge people, whether they walk the walk, not whether they talk the talk. And giving away millions and millions and millions of dollars to try to impact our political system so that we try to avoid the disaster of climate change, so that our kids' health isn't impacted by it, you know, I think speaks an awful lot to this person's character," said Lehane.
In the mad dash for control of the Senate, every dollar counts.
Majority Leader Harry Reid came to the Senate floor Thursday to rant, once again, against the Supreme Court's decision striking down overall contribution limits to political campaigns.
And that's when the Nevada senator suddenly started singing a populist fight song, that's not really on pitch with reality.
"The decisions by the Supreme Court have left the american people with the status quo in which one side's billionaires are pitted against the other side's billionaires. Except one side doesn't have many billionaires," Reid said.
The left doesn't have "many" billionaire backers? Besides Steyer, there's George Soros, David Shaw, and Irwin Jacobs to name just a few.
CNN's "The Lead with Jake Tapper" will continue to follow the money as the midterm elections approach. See our previous reporting on the conservative Koch brothers here.