Last week’s release of the redacted Mueller report, which has jump-started talk of impeachment among congressional Democrats, represents the greatest peril the Trump presidency has faced thus far. But its publication obscured a much subtler threat that also made its debut last week: the primary challenge of Bill Weld.

The former Massachusetts governor declared his candidacy on Monday as a Republican, though he served as the Libertarian Party’s nominee for vice president in 2016. John Kasich, Larry Hogan, and Jeff Flake have all muttered about launching anti-Trump campaigns of their own, like so many nerds vowing to confront their high school bully after one more drink, but Weld has the field to himself for now.

To call his bid quixotic is something of an understatement; his political persona is almost literally that of a modern-day Don Quixote, an aristocrat pursuing hopeless quests throughout the land in service of ideals that few besides him share. (He made a carpetbagging stab at becoming the governor of New York in 2006.) It’s possible that more voters will end up Googling the fisher—the savage weasel that Weld has impishly chosen as his campaign mascot—than his own record as a successful and popular governor of a major state.

If they did, however, they’d find that the Weld candidacy isn’t a joke, either on its own terms or as a response to Trump. No, he won’t win the nomination. But he is a politician of some principle, and he has spent most of his public life pushing back against the hard-right politics that reached its zenith in the current president.

Weld is a particular kind of Boston patrician, cut from the same cloth as the Saltonstalls, Peabodys, and Lodges who used to run local politics as a kind of white-gloved trust. Though his family line runs as deeply as any through the rocky New England soil, boasting generations of shipping magnates and Civil War heroes, he carries some meritocratic credentials as well. Not content merely to accept the family slot at Harvard, he went on to read economics at Oxford and graduate cum laude from Harvard Law.