It's a diacritic marker that indicates how the word is supposed to be pronounced, with a syllable break on the marked letters - as though readers might get confused and think the word is pronounced "reel-ection" as opposed to "re-election." It's a pretty archaic practice, but The New Yorker persists. They have a lot of unusual stylistic preferences, like preferring the spelling "vender" over "vendor," which also occurs in this article.
A more common example of the diaeresis would be the name "Zoë" - the "ë" indicates the pronunciation is "zoe-y" (2 syllables) not "zoe" (1 syllable).
As a Dutch person, what’s interesting to me is how this exact rule applies to Dutch. Maybe that’s why I didn’t notice it while reading the article…
til, thank you! i guess it's important for them we all coöperate on pröper spek :P
thought i was seeing this because some ebooks also have missing/poorly substituted ligatures for me