I think I realized a tactic by which you can always win elections.
Commit election fraud.
See, election fraud can sawy 20% of the vote. If you have a soild block of 30% of the people voting for you, you can just commit election fraud, and win.
Election fraud does make people a little upset with you, but also lower democratic expectations, meaning you won't have to worry about elections as much. In fact, commit election fraud as much as possible, even when you're winning, to lower democratic expectations. I'm not sure if the drop in respect caused by "election fraud" is enough to cancel out the increase in respect you get for holding elections in the first place, but I doubt it.
Election fraud is cheaper than bribing the faction leaders and giving out tax cuts. This is why it's far more perferable.
If you choose the trait, "BOUGHT THE ELECTION", you are able to sway up to 30% of the vote via election fraud. You only now need 20% legit support.
I also learnt that the best way of preventing elections is to have TV Stations and Newspapers blanketing the island. Set the TV Station to show "BBC" and Newspapers to print "Tropico Free". Those two programs will increase Liberty on your island, making your people feel free. Since the people are free, they are less likely to call for elections. You know, cuz they're free and all.