John Podesta, the veteran Democratic official, is leaving the White House to join Hillary Clinton’s 2016 Presidential campaign, probably as its chairman. The move was hardly unexpected: Podesta is a Clintonite through and through. He served in Bill Clinton’s White House from start to finish, rising through the ranks to become Chief of Staff, a post he held from October, 1998, to January, 2001. For months now, Podesta has been telling people that if Hillary decided to run he would most likely join her.

Now that Podesta has taken the plunge, it almost makes official what we already know: Hillary is in. And so are many longtime residents of Planet Clinton.

Even Podesta’s critics concede that he is an effective and experienced operator. Inside the Clinton Administration, he was known as a hard-working, intense figure with a caustic side. In a Times piece from September, 2000, Robert Pear and John Broder wrote, “Colleagues say, half-jesting, that he has an evil twin named Skippy, who is invoked to bring order to an unruly White House.”

A couple of years after the Clinton Administration ended, Podesta founded the Center for American Progress, a progressive think tank that, in a little more than a decade, has become an important player in the Washington power game, providing detailed analysis and policy recommendations, a forum for conversations and debates, and daily commentary on everything from the job figures to Bill Cosby. (Full disclosure: in 2013, I led a panel discussion at the launch of the Washington Center for Equitable Growth, which is housed at the Center for American Progress, and for which Podesta once served as chairman.) In January, 2014, Podesta left the Center for American Progress and joined the Obama Administration as a counselor to the President, focussed largely on environmental issues.

To the delight of environmental activists, when Podesta arrived back at the White House he championed the tactic of using executive power and the edicts of the Environmental Protection Agency to outflank Republican obstructionists on Capitol Hill. Last summer, the E.P.A. proposed a new rule designed to reduce carbon emissions from coal-fired power plants by up to thirty per cent. Other federal agencies, including the Department of Housing and Urban Development and the Federal Emergency Management Administration, have also stepped up their environmental initiatives. “I think he”—Podesta—“has made a tremendous difference,” former Vice-President Al Gore told National Journal’s Ben Geman. “I don’t think it, I know it.”

Some conservatives regard Podesta as an environmental extremist. From the left, the rap is that he is too close to major corporations and to Wall Street. In the late nineteen-eighties, when Podesta was working on Capitol Hill, he and his brother, Tony Podesta, founded the lobbying firm the Podesta Group, which is now one of the most successful in Washington. John Podesta hasn’t had a role in the firm for many years. But the Center for American Progress has faced accusations that it does favors for its corporate donors, most specifically in a May, 2013, investigative report by Ken Silverstein for The Nation.

The Center vigorously denies this charge. In a letter to The Nation, it said, “The inference at the heart of the author’s story is that corporate donations shape or drive the content of CAP and CAP Action. That assertion is baseless and completely false.” In December, 2013, the Center released a list of its corporate benefactors, which included Apple, Google, Walmart, Citigroup, and Goldman Sachs. The Center also pointed out that more than ninety per cent of its annual budget was financed through donations from individuals and philanthropic foundations, and that corporate donations accounted for less than six per cent.

My take on this flap is that with the Center for American Progress, as with any other think tank (or newspaper or magazine, for that matter), it is well worth keeping an eye on whether the folks who pay the bills are dictating the message. The Center would enhance its credibility—and this also applies to its competitors—if it more often promoted findings and policies that some of its financial backers and its political allies disagreed with.

That said, there’s quite a bit to recommend the Center’s activities, particularly its research initiatives and its Web site, which includes the lively (and editorially independent) ThinkProgress blog. Podesta’s efforts in founding the institution and getting it up and running filled a gap in the Washington ecosystem. Other liberal-leaning think tanks, such as the Economic Policy Institute and the Center on Budget and Policy Priorities, have long done sterling work. But, until the arrival of the Center for American Progress, which is now headed up by Neera Tanden, another Clintonite, no left-leaning think tank had the heft, the resources, and the drive of the conservative Heritage Foundation and American Enterprise Institute. (I am leaving out the Brookings Institution, venerable as it is, because it tends to stay above the fray, and also the New America Foundation, which is smaller and more narrowly focussed.)

Washington now has a big and well-financed progressive think tank that engages with the political debate on a daily basis. That’s a positive development—and not just for Democrats. On the basis of the theory of countervailing power, it’s good for democracy.

As Podesta sets out for 2016, it remains to be seen whether he will be an effective campaign chairman. Until now, most of his experience has been in administration and policy-making, rather than in political campaigning. But whatever services he provides to Hillary, he has already made a big mark on the political topography of the nation’s capital. And that, I’d wager, will be his longest-lasting legacy.