Open this photo in gallery: Students walk to attend the 374th commencement exercises at Harvard University, in Cambridge, Mass., on May 29.Brian Snyder/Reuters Harvard University is holding its commencement Thursday at a pivotal moment, when its place as one of the world’s leading higher education institutions is under what increasingly seems like existential threats from the Trump administration. Other schools face the loss of federal funding and their ability to enroll international students if they don’t agree to the Trump administration’s shifting demands. But Harvard, which was founded in 1636, a century and a half before the nation itself, is...