Clifford's nomination came in the immediate wake of the "Dred Scott v. Sandford" decision and was hotly contested. As a longtime partisan Democrat, the opposition labeled Clifford a political hack and a "doughface" — a Northern man with Southern sympathies. Anti-slavery representatives in the United States Senate fiercely opposed Clifford due to his pro-slavery record. They delayed his confirmation for thirty-four days, but were unsuccessful in blocking it completely. Clifford was confirmed on January 12, 1858, by a narrow margin of 26 votes to 23 in the Senate. If not for the Democratic Party rallying around their candidate, the absence of two of his opponents, and the last minute change in stance by a Democratic Senator, Clifford would have lost.