Over the last few months, Eric and Wendy Schmidt have quietly started a new philanthropic initiative that is shaping up to be an influential nerve center of the ultra-high-net-worth world. The effort, I have learned, is called P150—and it is already gaining traction among advisers to the mega-wealthy who want to co-fund new programs and share contacts and ideas, but also feel constrained by what some participants in the group call “single shingles,” or shops that serve a single donor without much staff. “Just about everyone I know is part of this community now,” said one consultant who was pitched on the org, with some amazement.