If a Sentence Equivalence sentence begins with 'Although the new policy was popular among voters, ____', the blank likely calls for a word that means

'Although' is a contrast signpost. It tells you the upcoming clause contradicts the first. If the first clause says voters liked the policy, the second must describe a downside. So the blank should be in the negative-valence family ('ineffective', 'controversial', 'flawed'). Picking a positive synonym for popular misses the contrast.