My first take on this is that this will simply add one page to an NSF application (which contains many forms/pages): Justify how your proposal relates to national security or the economy. While some have speculated that this means money will flow away from American Politics and towards International Relations and Comparative Politics, I am not so sure.* Yes, it is to justify the study of Militarized Interstate Disputes or Failed States under these criteria. Sure, studying International Political Economy or Comparative Political Economy will fit into this exception quite easily.
* I have applied to the NSF a few times unsuccessfully on grants dealing with the comparative and international politics of ethnic conflict. So, more money for me with this bill? Woot?
How about studies that focus on whether politicians represent their constituents' interests? Or the politics of climate change? These studies were the ones originally cited by the most visibily hostile folks (as opposed to Harry Reid who apparently is the most invisibly hostile until yesterday). I don't think it would take much work for an articulate grant-writer to suggest how climate change is an issue that affects the economy, or that democratic representation might have national security implications (do democracies that dis-serve their publics have more coups/riots/etc?).
Perhaps the Democrats folded once this exception was built in because they understood that the amendment thus became meaningless? I am not sure they are that clever. Ultmately, two things will shape the impact of yesterday's vote: (a) if the House also passes similar language and it remains in the legislation after the conference of the two Houses massage the differences of the bills; and (b) if passed in this form, it will matter if there is intense oversight and if the NSF director is a weenie. Regarding the latter: the NSF Director has to certify each Poli Sci (and no other subfield) grant addresses national security or the economy. The Director may choose to read this liberally or narrowly. The Congress may engage in heaps of oversight to make sure that the Director reads the exceptions narrowly. But if this is all symbolic politics, I am not sure Flake or Coburn will waste their time on this. Maybe. They have seem to think it plays well thus far.
I do suspect that one reaction is for Political Scientists to add token Sociologists to their grants and apply to the Sociology wing of the NSF.... If Congress only understood Principal-Agent dynamics, moral hazard and the like, they would understand that this is not the end of the story. But ignorance may be bliss for the Senators. Otherwise, why not fund research into how they do their jobs?