The rallying cry for Sumner and other Conscience Whigs throughout 1847 was the ongoing congressional debate over the Wilmot Proviso, the proposal to ban slavery in any territory acquired from Mexico. They made support of the proviso a minimum threshold for any future Whig candidate for president and threatened to break off and start their own party if Whigs failed to endorse it. But at the Massachusetts Whig state convention in the fall, Sumner was disappointed when party loyalists applauded Daniel Webster’s candidacy for the presidency in 1848, despite Webster’s failure to endorse the Wilmot
...more
