[richardtavor]

Refresh my memory. Why did Sessions recuse himself? For meeting with russian while still a Senator? And Senator Warner has not recused himself? Why no howling from the Public?

[Cboldt]

Sessions recused from investigating the Trump campaign because he was a close advisor to it. Roughly speaking, he has a vested interest in whitwashing investigations into himself and those he has political association with.

Sessions also recused from investigating Hillary because he would be viewed as having animus toward her.

Both are forms of "conflict of interest." The first one (campaign) is covered directly by DOJ conflict regulation.