What we’re hearing: White House counsel Pat Cipollone, who considers himself a civil libertarian, is expected to argue that the obstruction of Congress article is dangerous and could forever undermine the power of the executive office to protect privileged information.

Cipollone will likely frame the Senate trial as a defining moment to set the precedent for executive privilege, especially on national security matters, per a source familiar with his thinking.

This approach is something Cipollone is particularly proud of, and one that he is happy to test in court, the source said.

The argument: Presidential claims of executive privilege are especially strong when they involve conversations about national security.