I think it would be an interesting game mechanic to allow for early elections.
It could be game triggered based on low popularity. If playing with 3 parties and the player is in a coalition, this could be represented as a vote of no confidence. The player could be forced to give something big to the coalition partner in order to avoid the early election. If playing with 2 parties or if the player has a majority, it could be represented as a recall election (and this could be something the government could ban). This should require really low popularity (much lower than the no confidence vote), but there would be no option to compromise to avoid it.
it could be player triggered. If the player is doing very well in popularity, they could choose to trigger a snap election.
If the early election is triggered, either way, it should still be a few turns away. Basically the writ has been dropped, and the player can start the electioneering phase.
The player triggered one I think would be especially interesting, because it can be beneficial to trigger a post election boost, but if you trigger it too early it should probably make voters cynic and cost extra money.
What do others think? Would you find this mechanic interesting, or would it just be confusing? What other effects do you think triggering a snap election should cause?