@Barca- if the terrorists (or would-be terrorists) believe that they have affected a change, they will continue to use these same tactics and expect similar results. If I were a terrorist, my debrief would look like this:
1) the party that can help me realize my goals wins the election when they were the underdog
2) they won after I murdered 200 people (in the name of Allah, because Allah likes the blood from children)
3) therefore, mass murder before an election will sway an election

Nowhere in my logic does the question come up, "Why did the voters change their minds?" It's assumed - this happened, then this, then this.