Astorga’s campaign promises are apparently just an attempt to please voters.
Conclusion
Voters aren't being told what Astorga really plans to do if she becomes mayor.
Evidence
Astorga is telling voters that, if she becomes mayor, she'll do [all the things she's learned from opinion polls that voters want the new mayor to do].
Evaluate
How did the author think he proved that voters aren't really hearing what Astorga plans to do? This is a Comparison argument in which the author is assuming a difference.
The author assumes that what Astorga plans to do is different from what she's currently telling voters she'll do.
She seems to be cynically thinking that Astorga has her own plans for being mayor, and she is just looking at opinion polls and disingenuously lying to voters, acting like she's going to work on their wishlist, but she's really just saying that stuff to get elected, and then will proceed with her "real" agenda.
Goal
Look for an answer establishing the "assumed difference" -- i.e., Astorga doesn't intend to do the stuff she's currently telling voters that she'll do.
Or look for an answer that the author is clearly committed to thinking, something that, if negated, would badly weaken his argument.