In 1846, Representative David Wilmot of Pennsylvania proposed a measure in Congress that would prevent the expansion of slavery into the territories won in the Mexican American War. Wilmot's Proviso, as it was called, hoped to keep the territories open to white free labor as well as limit the power of Southern slaveholders, whose influence had come to dominate the Democratic Party. While the proviso passed in the House of Representatives because of the northern state's majority, the Senate remained divided between free and slave state Senators and thus never passed. The significance of the Proviso lay in how for the first time northern and southern politicians voted regarding their sectional rather than party interests.