The members appointed from private life under paragraph (1) of subsection (a) shall be appointed without regard to political affiliation; of each class of members enumerated in paragraphs (2) and (3) of subsection (a), two shall be from the majority party of the respective houses; of each class of members enumerated in paragraphs (4), (5), (6), and (7) of subsection (a), not more than two shall be from any one political party; of each class of members enumerated in paragraphs (5), (6) and (7) of subsection (a), not more than one shall be from any one State; at least two of the appointees under paragraph (6) of subsection (a) shall be from cities under five hundred thousand population.