This Pennsylvania Congressman kicked off a new round of sectional political conflict when, in August of 1846, a full twenty months before the United States actually acquired the Mexican Cession, he introduced his famous Proviso barring slavery from these lands. Southerners immediately took offense at the proposal, and defeated it. But a surprising number of northern Democrats voted with their section rather than their party on the measure. Their votes only confirmed many southerners' fears that the North harbored an unfair bias against slavery, and pushed them into increasingly aggressive demands for its protection. These actions pushed the nation into the sectional crisis that culminated in the Civil War.