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Until two days ago, Rod Rosenstein, the deputy attorney general, had an enviable reputation as a straight-shooting law-enforcement official respected by members of both parties. Then he decided that he was willing to help President Trump tamper with an investigation into his presidential campaign.

Now Rosenstein’s reputation is permanently damaged, as it deserves to be. In that damage is a lesson for other subordinates and allies of Trump.

When Rosenstein accepted his job at the Justice Department, many observers hoped he would be the adult who would moderate the excesses of Trump and Jeff Sessions, the attorney general. But it is enormously difficult to resist pressure, persuasion and incentives from one’s bosses, especially when those bosses are running the country.