Sentence:  With their apparently identikit backgrounds and bland politicians' patter, the contest has sometimes seemed an incestuous choice between <WSD>Tweedledum and Tweedledee</WSD>. When even the promised fratricidal war between the Miliband brothers failed to take off, one newspaper cartoonist illustrated a caricature of the contestants with the caption: Who cares who wins? 
Meaning of the word marked with <WSD> tags:  A pair of people who spend a lot of time together, and look and act similarly.