Besides almost certainly forfeiting a Senate seat that the GOP could have taken in November, Delaware’s Republican primary voters yesterday made a colossal mistake when it comes to education policy. Mike Castle is, and for two decades has been, one of American education’s wisest, sagest and bravest reformers.

I first came to know him in 1989 when, as governor of Delaware — and already a notable education change-agent there — he served as the first GOP governor on the National Assessment Governing Board (NAGB), which I then had the privilege of chairing. He came to Congress in January 1993 and my admiration for him has never flagged. He’s a workhorse, not a showhorse, the kind of pragmatist who actually likes to get things done — and is capable of reaching across the aisle for that purpose. His fingerprints are on every significant piece of federal education legislation of the past eighteen years. (And that’s not all he’s done in Congress.) He has chaired or served as ranking minority member of the main K-12 subcommittee of the House Education & Labor Committee for as long as I can remember, working with speakers from Gingrich to Pelosi, with committee chairs from Bill Goodling to George Miller, and with presidents from Clinton through Bush II to Obama. There have been one or two issues (e.g. Headstart reform) where I might have held out for more changes than Castle eventually settled for, but, as noted above, he’s a realist who would rather light a candle than yell into the darkness. (I’m sometimes guilty of the latter.) He learns from experience. He adapts to changing national needs and priorities (see, for example, his column on STEM education). And he has never failed to put the interests of kids ahead of those of adults.

At 71, he could retire but I hope he doesn’t. He’d be a superb university president, foundation chief, even U.S. secretary of education (if the crazies don’t also wreck the GOP’s chances of replacing Obama in 2012). Delaware and America have been well and honorably served and improved by his distinguished public-service career. Only a party with a death-wish would end it in this fashion.