Formally, matter is about population not ideology. Neither Mississippi nor Minnesota are large states, former has 5 House members and latter has 8. And southern control of Congress is not new, recall 'conserative coalition' of Dixiecrats and Reps that first reared its ugly head in 1937 over anti-lynching legislation. During era when seniority was absolute, southern Dems controlled floor leadership and committee chair positions. While V.O. Key may be correct that coalition was less pervasive than it sometimes seemed, Dixiecrat power stopped civil rights legislation for almost 2 decades (the coalition manifest itself about 30% of time in late 1950s and early 1960s when civil rights bills were on congressional agenda). Virginia's Howard Smith, who chaired House Rules Committee during that time, would go to his farm whenever civil rights legislation reached his committee, because the committee couldn't meet unless he called it into session his absence would result in bills being 'tabled.'
Of course, 'states rights' politics didn't apply when it came to channeling federal monies to southern states so long as legislation didn't include civil rights mandates. In redistributing economic resources from high-tax-base states to low-tax-base states, such policies meant that comparatively wealthier states subsidized small, economically poorer, rural southern states.
btw: there is contrasting view re. representation, some suggest that Electoral College bias favors more populated states - seventeen most uban states elect a majority of presidental electors but only 34 senators - and is 'check' on contrary congressional tendency. For what it's worth...
And yes, PNHP doctor's name is Quentin Young, Quentin Green was a doctor for some members of my family when I was growing up... Michael Hoover