Opposition from Cramer could also leave a Cain nomination deadlocked in the Senate Banking Committee, before it even reached the floor of the Senate for a vote.
The news of Cramer's opposition came as White House support for Cain also seemed to weaken on Thursday.
"Yes, we are, at the moment," National Economic Council Director Larry Kudlow replied when asked during an event in Washington about whether the White House still stood behind Cain, a former pizza executive and 2012 Republican presidential candidate. Kudlow is a former CNBC contributor.
"He's in the vetting process, we will see how that turns out," Kudlow added. "I don't want to prejudge it one way or the other."
A former 2012 GOP presidential candidate, Cain suspended his primary campaign in December 2011 after it emerged that three women had accused him of workplace sexual harassment, a fourth woman accused him of sexual assault, and a fifth woman came forward to allege that she and Cain had carried out a 13-year-long extramarital affair.
Cain has denied all the allegations. Still, the prospect of revisiting the allegations during a heated Senate confirmation hearing, and having to publicly defend Cain, likely holds little appeal for the White House or for Republican senators in swing states.
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