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New working paper from Stuart Perrett, @drjennings.bsky.social , @jonmellon.bsky.social , @cbwlezien.bsky.social and me: Do polls underestimate support for right-wing parties? Assessing variation in polling error by party family osf.io/preprints/so...

Using ~8.5k election-poll-party observations from 372 elections in 32 countries, we find a persistent partisan asymmetry: polls tend to overestimate the left relative to the right. On average across elections, polls the month before an election overstated the left by about 1.4 points

Breaking it down further by party family, we see a fairly consistent pattern across the left party families but more variation on the right, with polls tending to underestimate Agrarian and Conservative parties, but not Christian Democratic and Far Right parties.

Obviously, 'on average' doesn't mean polls are always-and-everywhere biased to the left - there is a lot of heterogeneity between elections - but elections are much more likely to have a leftward polling bias than a rightward one.