The preponderance of New York Barnburners present at the [Wilmot] proviso's creation . . . is worth noting here. Six of the eleven instigators of the proviso . . . were either New Yorkers or members of Barnburner leader Preston King's mess in Washington. Each was a Van Buren Democrat.
Jonathan H. Earle, Jacksonian Democracy & the Politics of Free Soil, 1824-1854.
Next, we'll take a closer look at Mr. King.