Election fatigue is a concept raised in several works in electoral studies. I'm thinking, for example, of my work with André Blais, but also André Blais' work with Filip Kostelka, and a more recent article by Alex B. Rivard and other colleagues on the Canadian code.
Election fatigue refers to the fact that the number of elections and their proximity to each other make citizens less inclined to participate. All sorts of political attitudes may be affected, but interest in politics is less likely. This interest in politics is crucial because it's one of the best predictors of why people vote, but also other things like a sense of civic duty.
I conceive of voting as being a duty before being a right or a choice. I do my civic duty by voting in federal elections, and I vote in municipal elections because I still see it as a civic duty. On the other hand, if I've already voted a few days ago at the federal level, and now it's time to vote at the municipal level, perhaps I'll be a little lenient with myself and tell myself that I've done my civic duty and that I'll pass this time for the municipal level in Quebec.
Election fatigue therefore has an undeniable negative effect on voter turnout, an effect that is reflected in various political attitudes, including interest in politics. People become less interested, more tired. They have less energy to engage politically in discussions or to go out and vote.