If there is a major terrorist atrocity during an election campaign, there's a good chance the incumbent party is stiffed whatever happens. But what you *don't* do, is deliberately lie about who dunnit.
IMO that remains the major political lesson from these terrible events two decades ago.
Or you could say this:
Senior US officials said voters had appeased terrorists by rejecting Jose Maria Aznar's government - a key US ally in the war on Iraq.
http://news.bbc.co.uk/2/hi/europe/3572565.stm
Such ridiculous Bush era rhetoric when what happened was it backfired on PP that they blamed ETA rather than Al Qaeda.