What type of person would have supported the wilmot proviso?

The Wilmot Proviso aimed to ban slavery in territory acquired from Mexico after the Mexican American War.

Those that were supportive of the Proviso were American citizens who were 1. opposed to the institution of slavery and 2. wanted to force the issue of slavery as a national issue. #2 is especially important as during this period, many were hoping to ignore the national issue of slavery or at least keep it from becoming the dominant national issue.