While backing and opposition to Warsh fell largely along party lines, Senator Thom Tillis was the lone Republican to withhold support.
Tillis, who is not running for re-election, said he actually backs Warsh’s appointment to the role, praising his “extraordinary credentials”.
But the North Carolina senator said he wants an inquiry into outgoing Fed chairman Jerome Powell to be dropped before he will vote to approve his successor.
Trump has frequently clashed with Powell over monetary policy.
The probe relates to an overspend on renovations to the Federal Reserve building.
Tillis said the cost overruns, while “unfortunate”, were “legitimate”.
Powell plans to remain in post beyond the date his term ends, 15 May, if Warsh is not confirmed. Tillis’s ongoing blockade could make that prospect a reality.