And electoral frustration is also probably a factor in the current nail-bomb attacks.

ECONOMIST: Crime

The homemade, nail-laden bomb, which investigators say was designed to kill people rather than merely damage property, exploded outside of the clinic's front door Thursday morning.

CNN: Search continues for witness in clinic bombing

President Obama was slow to see the pattern, but after three nail-biting suicide negotiations in two years, he seems to have finally realized that he cannot continue to encourage the bomb threats with concessions.

CNN: GOP's obstructionism is suicide strategy