In Britain on a trade mission, Wisconsin Governor Scott Walker was quizzed about foreign policy at a session at London’s Chatham House. But rather than say anything that might help bolster the potential 2016 candidate’s foreign-policy credentials, Walker channeled mid-20th century Senate giant Arthur Vandendberg and acted as if partisan politics really should stop “at the water’s edge” and avoided saying anything that might be taken as a criticism of President Obama or even an opinion about various world crises. That might be considered principled, but if Walker wants to actually win his party’s nomination he’ll have to do better in the future (as well as avoiding being trapped into giving equivocal answers about his belief in evolution). That the exchange happened the same day that Congress began considering the president’s proposal for a new war powers resolution authorizing the use of force in the Middle East also means the same lesson will apply to other candidates. Though conventional wisdom tells us that economic questions will always dominate presidential elections, the rise of ISIS has ensured that anyone who is thinking about the White House needs to have a coherent vision of American foreign policy.

As our Max Boot termed it, Obama’s proposal for authorizing U.S. actions against terrorists in the Middle East is “a classic muddle.” By attempting to balance the administration’s allergic reaction to a U.S. commitment that might actually defeat ISIS while providing a legal basis for its ongoing half-hearted efforts, the president has provoked criticism from both the right and the left. But rather than being a compromise that makes sense, it merely confirms for those who weren’t already convinced that the president has no real strategy for eliminating ISIS or even for significantly “degrading” it.

It’s not clear what exactly will come out of the Congress as both House and Senate leaders struggle to come up with a formula that makes more sense than the administration’s attempt to set up one with limitations that ensures the U.S. can’t prevail in the conflict. But while his critics may demand that the president demonstrate that he has a path to victory over ISIS, they have very little leverage over his choices. No matter the outcome of the votes on a force authorization, nothing can make the president prosecute this war with conviction. Indeed, the U.S. is increasingly showing signs that the president is more interested in making common cause with Iran than in actually rolling back ISIS’s vast territorial gains in Iraq and Syria. That means the connection between Obama’s equivocal approach to the nuclear talks with Iran is not only worrisome in and of itself but a sign of an overall strategy in which the U.S. will acquiesce to Iran becoming a nuclear threshold state and obtaining regional hegemony in return for cooperation against ISIS.

All this makes it even more important than it normally might be that potential 2016 GOP presidential candidates have more to say about foreign policy than platitudes. In 2008 the presidential contest—or at least the Democratic nomination that year—was essentially decided on the basis of Barack Obama’s adamant opposition to the Iraq war. Yet every new ISIS atrocity and terror attack is going to make it harder for anyone—whether on the right or the left—to run on a platform of keeping the U.S. out of the Middle East or to avoid conflicts.

For Democrats, this might make it even harder for those outliers with the temerity to challenge the Hillary Clinton juggernaut to get some traction by outflanking her on the left with another anti-war campaign. For Republicans, the more attention paid to ISIS murders of Americans, the harder it will be for Rand Paul to break out from the ideological box that his libertarian isolationist base has put him.

Nevertheless, Republican candidates need to do more than merely carp at Obama or issue ringing rhetoric about fighting terror. Unlike in 2008 and 2012, when many Americans thought they were electing a president to get them out of unpopular wars, the force authorization vote ensures that whoever wins next year will be leading a war effort that may well dominate their presidencies.

Unless something very unexpected happens in the next year, Republican candidates will be competing in primaries where they will be expected to tell us how they are prepared to beat an enemy that is, contrary to President Obama’s assurances, very much not on the run. That gives an advantage to a candidate like Senator Marco Rubio, who has been speaking with some authority on foreign policy throughout his first term in the Senate. Jeb Bush will have to also show whether his approach to foreign policy is, as some reports have indicated, a knockoff of his father’s “realist” policies that may not provide much of a contrast with Obama’s equivocations. By contrast, it puts those GOP governors that many of us have been assuming will be formidable candidates on the spot to quickly get up to speed on foreign policy. Walker is not the only one who fits in that category, but after his recent surge in the polls in Iowa, it’s obvious that if he wants to stay on top, he’s going to have to say something more than “no comment” about Iran.