Washington, July 11 -- Some are watching old video of his previous testimony. Others are closely re-reading his 448-page report. And almost all are worrying about how they'll make the most of the short time they'll have for questioning.

Robert Mueller, the Democrats know, will be tough to crack.

The stern, reticent former FBI director has said he won't answer questions beyond what is in the report on Russia's election meddling and the Trump campaign and possible obstruction of justice when he comes to Congress on July 17.

Mueller is expected to testify in front of the Judiciary and intelligence committees for two hours each, with time split evenly between Republicans and Democrats, though that timing is still a subject of negotiations....