“No one is above the law,” said House Speaker Nancy Pelosi as she announced the Democratic effort to impeach President Trump over the Ukraine matter. The phrase has become a Democratic mantra in the new impeachment push. But it could, in the end, serve to highlight the weakness of the Democratic strategy.

The reason is, by stressing that Trump is not “above the law,” Democrats are basing their case against the president on the argument that he broke the law and must be held accountable. But it’s not at all clear that Trump broke any laws in the Ukraine matter. In the face of a vigorous Republican defense, any argument on that question is likely to end inconclusively.