Nativists Are Not Complete Idiots
According to Iain Murray, the recent Spanish elections were marked by an increased turnout and left-wing voting among first-time voters. I'd like to know how many of those voters were either Muslim immigrants or their children. There may have been a voter-registration drive in Spain's Muslim community. It's even possible the terrorists planned their operation in order to provide cover for an electoral takeover. That might explain the attitude of Spanish conservatives that the election was somehow stolen.
On the other hand, maybe a nation with as low a birth rate as Spain deserves to be taken over.