Caleb B. Smith, Secretary of the Interior, straddled the question of relieving Sumter, but distinctly leaned against the attempt. He contended that the expedition would encounter resistance, and even if it managed to provision Anderson, the garrison would be unable to hold out against the enemy once conflict had started. Only a massive reinforcement of the fort could make it defensible, and Fox's plan had a more limited objective. Further, the fort served no significant military purpose for the government.
As for the political issues raised by Sumter, Smith was less clear. On the one hand, he asserted that if abandoning the fort was regarded as an admission that the government could not enforce the laws, "I should without hesitation advise that it should be held without regard to the sacrifices which its retention might impose." But Smith offered his opinion that the abandonment of the fort would signify no such thing. He implied that the public would understand that the Buchanan administration had left Lincoln with no recourse but to abandon the fort, or risk lives and, perhaps, war.
The government, Smith advised, should vindicate its power and honor in other ways. If the United States looked like the aggressor, public opinion in the North would be divided, while "treason" in the South would be openly encouraged.
Bibliography: Lincoln, Works, eds. Nicolay and Hay, 6: 210-14.