Kinley Brauer, "Davis, John," American National Biography Online, February 2000, http://www.anb.org/articles/03/03-00129.html.
Davis was one of the two senators (along with John M. Clayton of Del.) who voted against the declaration of war against Mexico on 12 May 1846. On 12 August 1846 he spoke at such length in favor of the Wilmot Proviso, an amendment to a military appropriations bill that stipulated that no territory acquired from Mexico would be open to slavery, that the Senate had no time to vote. The bill had already passed the House. Davis later explained that he had intended to speak long enough to leave time only for a vote, which he thought would be positive. He doubted opponents of the proviso would refuse needed military appropriations and delay peace negotiations, and he claimed simply to have misjudged the time. Scholars remain divided on the plausibility of Davis's explanation and whether the bill would have passed had it come to a vote.