To little fanfare, the super PAC founded by liberal climate change activist Tom Steyer has amassed $13 million of the California billionaire’s own money this election cycle — so far. That outpaces the $9.3 million Steyer gave his outside group, Next Gen Climate Action Committee, by this point in 2014.

Very little of that money has gone toward directly influencing the presidential race, however. Though he’s the biggest liberal megadonor so far this cycle, unlike George Soros and Haim and Cheryl Saban, Steyer hasn’t contributed money to Priorities USA Action — the super PAC supporting Hillary Clinton’s presidential campaign. Soros and the Sabans have personally given Priorities $7 million and $5 million so far, respectively.

Ultimately, NextGen funneled $19.5 million directly into 2014 congressional midterm races to urge the public to vote for or against certain candidates. That year, Steyer’s contributions to the super PAC totaled $66.9 million and the group spent about $65 million of that. He also gave $5 million to a mainline Democratic outside spending group that year, Senate Majority PAC.

Now, Steyer’s $13 million in contributions, as of the end of January, to NextGen alone have placed him at the No. 2 spot on the Center for Responsive Politics’ranking of megadonors in 2016. He runs just behind Long Island hedge fund manager Robert Mercer, who has already given millions to conservative outside groups, including one $11 million contribution last year to a super PAC supporting Sen. Ted Cruz‘s(R-Texas) presidential campaign.

The super PAC has yet to spend any money so far this cycle promoting or opposing candidates, but has laid out more than $17 million already for expenses like digital advertising and direct mail, as well as for issue-based TV ads that don’t mention candidates. Much of the digital advertising money has gone to a company, Bully Pulpit Interactive, that counts the Democratic National Committee, the Democratic Senatorial Campaign Committee and the Democratic Congressional Campaign Committee among its clients.

Steyer is, essentially, a single-issue donor, much like another left-of-center megadonor, Michael Bloomberg. NextGen Climate Action Committee, as well as its dark money affiliate NextGen Climate Action, focuses on influencing the national conversation around climate change and encouraging lawmakers to adopt clean-energy policy positions.

Both men have remained relatively independent of the nation’s leading Democrat, Clinton. The sole exception is Steyer’s $250,000 gift to American Bridge 21st Century — a Democratic opposition research group that is now solely focused on Clinton’s election — last year.

Clinton has pushed a clean energy agenda on the campaign trail. But her base of big donors tends to comprise mainly people that she and her husband, former President Bill Clinton, have had longer relationships with; Steyer only burst onto the political money scene in a big way in 2014.

During her term as Secretary of State, Clinton maintained her contact with wealthy donors who had funded her campaigns before and to whom her lieutenants running Priorities could eventually go for funding, a review of her emails released as part of a FOIA lawsuit shows.

Steyer’s name never appears in the trove of emails the State Department has released from Clinton’s private email account over the past year, the last batch of which was made public Monday. The three biggest liberal donors besides Steyer — Soros and Saban, as well as Bloomberg, the former New York City mayor — all show up in Clinton’s emails.

Records show that Clinton’s aides discussed meetings with Soros and that she met with him to discuss his offer to match the amount of government funding dedicated to an American university in Central Asia; he apparently said, after a second meeting with her, that he regretted supporting President Obama in the 2008 Democratic primaries. Haim Saban himself wrote to Clinton’s account at clintonemail.com, once apologizing for a miscommunication and adding, “Very much was looking forward to hangin’…tx again for today. Love u.”

Clinton responded, “Not to worry. Loved seeing you and Cheryl and looking forward w Bill to the White House tonight. See you then–H.”

Bloomberg, has given $5.4 million to his own super PAC, Independence USA PAC, this cycle. By this point in 2012, Bloomberg had given $2.9 million to his outside groups. His name appeared in a 2012 email about a trip the mayor planned to Vietnam; Clinton aide Cheryl Mills said she connected the Bloomberg staffer to two people in response to his desire for state to facilitate a meeting.

Earlier, Clinton and her aides had discussed Bloomberg’s involvement in the 2010 Shanghai Expo, for which they desperately needed funding and received support from old Clinton hands.

Steyer made his money as manager of a hedge fund, an industry that handily gives the most money to outside groups and has thrown serious weight behind Clinton — as well as some Republican candidates. A request for comment from NextGen Climate Action were not returned by the time of publication.