The tragic events in Spain may have undesirable political implications for Kerry. Here's why. The Republican attack machine is increasingly desperate in their attempt to portray Kerry as bad for national security.
So, what they are going to do is try to paint him as the candidate that the terrorists want to win the election. This has become easier to do with the recent statement from Spain's Prime Minister Elect that US voters should follow the Spanish example. Whether it is valid or not, Spain is being labeled as a "terrorist appeasing" nation. The Republicans will almost certainly seek to paint Kerry as the terrorist appeasing candidate. If Middle America buys into this, he'll lose his edge in the polls.
To combat this, Kerry must make it 100% clear that he will fight terrorists as aggressively as the Bush Administration claims that it has over the past few years. To do this, he can bring up the action against the Taliban in Afghanistan and say that he and most of the world agreed with Bush that attacking the Taliban was justified and necessary. Next, he can paint Bush as someone who became obsessed with overthrowing Saddam - distracting from our mission in Afghanistan and the hunt for Al Qaeda suspects and alienating the United States from its allies. In doing so, he can "praise" Bush (to demonstrate bipartisan spirit) for a strategy of attacking terrorists (as was the case in Afghanistan) while at the same time highlighting all the ways that the Administration has undermined the war on terror (giving Al Qaeda a central theme to use for recruitment, shifting military resources to the Iraq war, alienating us from our allies, breaking the national budget and thereby forcing a cut in spending on homeland defense, etc). He can point out how Bush moved the hunt for terrorists to the back burner while he was stumping for his war in Iraq (demonstrating bad priorities). Then he can show how Bush distorted and pushed questionable evidence to build support for the Iraq war (demonstrating obsession). This will give Kerry a chance to distinguish himself from the Bush camp with respect to terrorism without coming off as a dove. Once the distinction has been made, it can be repeated over and over again at virtually every campaign event.
In short, Kerry must make it clear that he will fight terrorists with all the enthusiasm of the Bush Administration and then some, but in doing so, he can also make it clear that he would not have let Iraq take away from the fight against Al Qaeda. There is a distinction between the candidates on the issue of terrorism. Republicans are trying to define it as "Kerry is the man that terrorists want in the White House." We know better and we can't let them do this. This is just a rough draft of my ideas on the matter. I'd love to hear your thoughts as well.