For those looking for the hidden hand of politics in what the Supreme Court does, there’s plenty of reason for suspicion on Donald Trump’s as-yet-undecided immunity case given its urgency. There are, of course, explanations that have nothing to do with politics for why a ruling still hasn’t been issued. But the reasons to think something is rotten at the court are impossible to ignore.On Feb. 28, the justices agreed to hear Mr. Trump’s claim that he is immune from prosecution on charges that he plotted to subvert the 2020 election. The court scheduled oral arguments in the case for...