The annexation of Texas was the chief political issue of the day. Van Buren, initially the leading candidate, opposed immediate annexation because it might lead to a sectional crisis over the status of slavery in the West and lead to war with Mexico. This position cost Van Buren the support of southern and expansionist Democrats; as a result, he failed to win the nomination. The delegates likewise could not settle on Lewis Cass, the former Secretary of War, whose credentials also included past service as a U.S. minister to France.