On immigration, Mrs. Clinton could easily have said that she would work to pass comprehensive reform legislation and defend President Obama’s existing orders forbidding deportations. Instead, she told a Las Vegas crowd last week that “if Congress refuses to act, as president, I would do everything possible under the law to go even further.” Mr. Obama’s going beyond the law on immigration is already quite problematic, and her eagerness to go further than he has is alarming. The answer to lawlessness is not greater lawlessness. Unless you’re a Clinton.

As for President Obama: I’m baffled by his attack on Sen. Elizabeth Warren in a Yahoo interview last weekend over her opposition to granting him trade-promotion authority. Mr. Obama claimed “her arguments don’t stand the test of fact and scrutiny,” rejected her logic by snapping he would “have to be pretty stupid” to do what she alleges, and then dismissed her by saying, “the truth of the matter is that Elizabeth is, you know, a politician like everybody else.” By having her intelligence, judgment and motives questioned, Ms. Warren is getting a taste of what it has been like to be a Republican in the Obama era.

More important, the president’s harsh language made no strategic sense. It certainly contributed to Senate Democrats’ decision to block (perhaps temporarily) trade-promotion authority on Tuesday. Beyond that, his assaults elevated Ms. Warren while needlessly weakening the president’s standing on Capitol Hill. Mr. Obama poisoned his relations with congressional Republicans through personal attacks, and he now is doing the same thing with congressional Democrats. Why?