For most of the 20th century, Missouri's Democrats were in St. Louis, Kansas City and the rural Southern part of the state.
The rural Southern party of the state swung Republican with the rest of the South.
St. Louis and Kansas City have been stagnating or declining in population for the past several decades and exercise less and less clout within the state.
Not southwestern Missouri though. I think that has long been Republican like northwestern Arkansas.
I think he was referring to Southeast Missouri (or the Bootheel, as some non-Missourians refer to it). If you look at a map of the current districts in the Missouri House of Representatives, you'll see red everywhere except in and around St. Louis and Kansas City, and Columbia to a lesser extent. There's only about four splashes of blue outside the main urban areas, and three of these are in Southeast Missouri: you have District 118 represented by Ben Harris which contains some of the Lead Belt around Washington County as well as some sections of Jefferson County; District 117 represented by Linda Black which is based in St. Francois County, also part of the Lead Belt; and District 149 represented by Steve Hodges which is based in the Bootheel counties of Mississippi and New Madrid. These are some of the handful of rural areas in the state that have not completely abandoned their Democratic roots; the right kind of Democrat can still win in these counties and still do (see Jay Nixon, Claire McCaskill, etc.)
