The last of these, the carbon tax, is a good idea and a hard sell in itself. But the total package is not a platform that Democrats can run on—it’s a platform they’re going to run from. And it is a fantasy-come-true for Republicans. For decades, they’ve been falsely accusing Democrats of favoring huge tax increases. In this case, it would be the truth.
 So far, many Democrats have hardly registered the full significance of what Sanders’s candidacy would mean for their party. But I don’t think Republican strategists have missed the possibilities. A Sanders nomination would be their opportunity to capture decisive control of all branches of the federal government from a divided and weakened Democratic Party. Among other things, Republicans would be able to consolidate a Supreme Court majority for a long time to come. As those who supported Ralph Nader in 2000 should recognize now, the costs of purity can be heavy indeed.