Provided Rep. Ron Paul (R-Tex.) is not the Republican nominee, Republicans will have the opportunity to challenge the president on national security. However, to do so successfully, the nominee will need to wield a scalpel and not a hack saw.

Certain items in the administration's policy choices that were liabilities a year or so ago are no longer fodder for his opponent since President Obama has essentially caved and adopted Bush-era policies. He, for example, has agreed not to try Khalid Sheik Mohammed in federal court and has signed off on the Defense Department authorization bill that gave the United States broad latitude to detain enemy combatants. Gitmo remains open. There is no reason to deny him credit for acting upon intelligence developed by two administrations to kill Osama bin Laden.

Aside from these issues, though, there is plenty in his performance on foreign policy to take issue with. The president’s rash decision to pull all troops out of Iraq and put Afghanistan on an election timetable are grounds for criticism — indeed, outrage. News that Gen. David Petraeus considered resignation to protest the president’s withdrawal schedule in Afghanistan confirms the degree to which the process was dominated by political instead of military concerns.

Obama also is exceptionally vulnerable with regard to his irresponsible defense cuts. Former defense secretary Robert Gates was required to serve up round after round of cuts, leaving the military in a precarious position. Obama’s failure to avert the sequestration of defense spending, which his current defense secretary declared would harm national security, should be sharply challenged.

It is Obama’s continued conduct with regard to totalitarian regimes, however, that is his most dangerous legacy. He relaxed sanctions on Cuba; Alan Gross rots in prison. He turned a blind eye toward the Green Movement; the mullahs move closer to a nuclear weapons capability, despite sanctions (which turned out to be less than crippling). He pulled anti-missile sites out of Eastern Europe and signed the START agreement; Russia’s human rights abuses have increased and its scientist facilitated Iran’s nuclear weapons progress. He tried to engage China and avoid confrontation on human rights and cyberterrorism; China’s human right atrocities have multiplied, and its military build-up proceeds apace.

It is important for the nominee to make his arguments on the specific failures (e.g. his settlement fixation brought the “peace process” to a halt) rather than impugn Obama’s motives (“he hates Israel”). General-election voters shouldn’t be forced to conclude that the president is malicious in order to conclude he has made the United States and its allies less secure. Simply judging him by his results should be sufficient to make the case that he’s reduced American influence in the world by wrongheaded policies.

Finally, Republicans fervently believe that Obama desires to reduce America’s visibility in the world and constrain itself by acting primarily through international bodies. Whatever he believes about American exceptionalism, the fact remains that treading water while waiting on the United Nations or Arab League has resulted in thousands of deaths (in Syria and Libya) and reduced American influence and credibility dramatically.

There is plenty of material available on the foreign policy front for the GOP nominee to use. However, a heavy-handed or sloppy assault will forfeit whatever advantage Republicans may have in this area. The GOP nominee should not eschew foreign policy discussion, but neither should he allow Obama to claim the high ground by an ill-conceived attempt to convince Americans that Obama isn’t concerned with America’s national security. Rather than arguing Obama acted in bad faith, it is more effective and convincing to argue he made bad decisions based on an incorrect assessment of the world.