Most blue Democrats seen in dubious seats (7)
I believe the answer is:
saddest
'most blue' is the definition.
('sad' can be similar in meaning to 'blue')
'democrats seen in dubious seats' is the wordplay.
'democrats' becomes 'dd' (a political abbreviation for democrat repeated).
'seen in' means one lot of letters goes inside another.
'dubious' indicates an anagram.
'seats' with letters rearranged gives 'saest'.
'dd' put within 'saest' is 'SADDEST'.
(Other definitions for saddest that I've seen before include "Most doleful" , "Most gloomy" , "Unhappiest" , "Most unhappy" , "Most blue" .)