Yes, you're right, they do seem to play this up. That's strong evidence against the conspiratorial explanation I mentioned.

people's votes tend to shift "rightward" when they are afraid for their lives

Yes, I think this is true. But I seem to remember (but cannot cite) that people also "rally around the flag" and support the leader more--even if the leader is not "right."

Moreover, the present government still has some additional political incentive to play up the risk of terrorism, especially if the administration can blame it on the previous one. "Al-Qaeda is really scary--man, our predecessors sure did let their guard down."