WASHINGTON For the second time in less than two years, President Donald Trump is poised to fill a Supreme Court vacancy. But hes not the one remaking the nations most powerful court for generations of Americans. Its Leonard Leo.

Leo, executive vice president of The Federalist Society, a national organization of conservative lawyers, has played a central role in the selection and confirmation of three Supreme Court justices: John Roberts, Samuel Alito and Neil Gorsuch. And on Wednesday, Leo announced that hes taking leave from his job, effective immediately, to personally advise Trump on a replacement for retiring Justice Anthony Kennedy .

Trump plans to pick someone from his previously released list of 25 potential Supreme Court nominees a list that Leo put together for him, at Trumps request. If all goes as planned, Leo, 53, will have helped secure his fourth justice on the court by the early fall.

No president in modern history has had this kind of influence in reshaping the Supreme Court. Leo doesnt singularly deserve credit for putting these judges on the court, of course; it takes teams of people to get a nominee through. But long after Trump is out of the White House, Americans will be feeling the effects of a court stacked not by any particular president but, in large part, by Leo.

Its incredible, said Carl Tobias, a law professor at Virginias University of Richmond and an expert on judicial nominations. Certainly, hes had an outsize influence for any one person. I know President George W. Bush relied on him a fair amount for two nominees, and in this administration, I dont think theres ever been anything quite like it.