In the UK under FPTP atleast, I can imagine there is also an effect or reverse gerrymandering or similar. When it comes round to elections, generally the resul

In the UK under FPTP atleast, I can imagine there is also an effect or reverse gerrymandering or similar. When it comes round to elections, generally the result of the majority of seats is already known, so they're classified by parties into stronghold (ours), stronghold (theirs), marginal. When your located within a Labour stronghold, your unlikely to see as much pro-Conservative media, as they are better off spending their time campaigning in marginals and defending their reputations in existing strongholds. Surely, this effect simply compounds strongholds, making them even harder to change hands overtime, without a significant event to cause the public opinion to shift significantly (e.g. the Scottish independence referendum). The only way to fix such a problem, would be to randomise the boundaries each election, but this would cause various extra complexities.