Ultimately, it came from Donald Trump.
Since Obama re-appointed Rosenstein twice as U.S. Attorney for Maryland, and since only six Democrat Senators opposed Rosenstein for Deputy Attorney General, the big question is:
“What was Trump thinking?”
Trump had more than two months to withdraw Rosenstein’s nomination after Sessions recused himself.
But - Trump did nothing.
I get that, but who was involved in the initial selection and vetting process? (And why does Session seem to love him still?)