The Campaign Trail really is the best presidential campaign simulator available. The choices you make seem real, imply tradeoffs and dynamically affect the story and events of the campaign. It satisfies the deep itch that players like us want: role-playing, as opposed to dressed-up spreadsheets and mathematic resource-management that underly games like President Infinity.
This actually hits the nail on the head with PI; I've only ever had one game where I felt a genuine challenge (was Guilani running in 08 against Obama and I must have dumped about £70 million into NY only to lose it by 1% while narrowly losing Virginia & Michigan)
The game eventually becomes stale; even as a low ranking candidate you just camp out in Iowa and watch yourself climb before getting a boost before Super Tuesday. The AI spends money at a stupid rate so you always end up facing bankrupted opponents
