4. What Sessions' resignation means for the Mueller investigation

The details: The deputy attorney general traditionally assumes the acting role as the country’s top law enforcement official upon such a departure.

• Rosenstein has been overseeing the special counsel’s investigation after Sessions recused himself due to his close ties with the Trump campaign.
• However, Whitaker will now assume control of the investigation, according to a DOJ prosecutor.
• He had questioned the scope of the Mueller probe, arguing in a CNN op-ed last year that the special counsel had gone too far in explaining the Trump family’s finances.

“This would raise serious concerns that the special counsel’s investigation was a mere witch hunt.”

The big picture: Rosenstein has largely been seen as a barrier protecting the Mueller investigation from Trump’s interference. As Susan Hennessey and Benjamin Wittes of the Lawfare Blog explain, Rosenstein "has assiduously defended the Mueller investigation, even as the president has decried it as a ‘witch hunt,’ even as congressional committees have pressed for unprecedented document releases by way of discrediting it."

What's next: With Democrats fresh off a midterm campaign victory in taking control of the House, they will continue to express their frustrations over Whitaker's new role and the urgent need for congressional action to protect Mueller. They've already warned that Whitaker's previous remarks about Mueller suggest he is unfit to oversee the investigation.