It's reasonable to at least expect that. It's their job after all, while for any single voter there is a lower standard you can realistically hold them too and less time available to verify/debunk claims.

On top of that, there are also instruments that help the voters track whether politicians are engaging in corrupt lobbyism like voting records + donation / campaign contribution records, though few countries do that to a degree that it forms a cohesive anti-corruption framework. None of those measures exist for individual voters.