Nikolas Gvosdev thinks about how foreign policy issues might affect and be affected by the approaching midterm elections:

A comprehensive deal that “solves” the Iran nuclear imbroglio could be a major boost for Obama, validating his approach to world affairs and discrediting those who argue that only military confrontation can produce a satisfactory resolution to the Iranian nuclear stand-off—and other crises. Indeed, the administration might push for a comprehensive deal with Iran in order to contrast the success of Obama’s cautious approach to war with the failures of Republican approaches. A similar logic undergirds the current push for restarting the Israeli-Palestinian peace process and might also serve as the basis for a U.S. diplomatic push to reduce tensions in the East and South China seas.

On the other hand, diplomacy, if spun as “concession” or “weakness,” might damage the Democrats’ electoral chances, particularly on the Iran issue, where there is enormous skepticism as to the good faith of the Islamic Republic to implement any agreement.

All of this makes sense, but it seems more likely that the midterms won’t be significantly influenced by international events and foreign policy either way. Barring a new attack on the U.S. or Americans overseas or the eruption of a major conflict somewhere in the world, foreign policy will matter even less to most midterm voters than it did to voters in the 2012 election. There have obviously been midterm elections in the recent past where national security and foreign policy issues were top priorities for many voters (e.g., 2002 and 2006), and they did contribute to the success or failure of the president’s party, but those elections took place in the wake of 9/11 and during the worst year (at least for the U.S.) of the Iraq war. So far, there is nothing like either of these that will influence the midterms. As unpopular as the war in Afghanistan is, it doesn’t appear to be a major factor driving Republican gains this year.

The most important effect that an Iran deal–or the failure of one–could have on the election is how it changes Obama’s approval rating, if it changes it at all. If negotiating with Iran contributes to a declining approval rating, that will also drag down the president’s party, and that will increase the number of Senate seats that the Democrats lose. Since the public has so far been mostly supportive of diplomacy with Iran, and in most polls has expressed support for the interim deal, I don’t think we should expect that to happen. In specific Senate races, having to defend the nuclear deal may be a liability for certain Democratic incumbents that already face tough challenges. It would almost certainly make things more difficult for Mark Pryor in Arkansas in his race against the extremely hawkish Tom Cotton, but he’s already on track to lose that race. There are not any competitive races this year that I can see where the nuclear deal would be an obvious boost to the Democratic candidate, but those most likely to object to the deal were already going to vote for the other party anyway.

We should also bear in mind that the midterms could have an unfortunate effect on diplomacy with Iran. Since the Republicans are likely to take control of the Senate, that could factor into the calculations of other states when they consider Obama’s ability to follow through on U.S. diplomatic commitments. If the Iranians assume that a Republican-controlled Senate would press ahead with additional sanctions legislation or perhaps even an authorization of force resolution, they may conclude that reaching a deal with the U.S. before the election is a mistake. Needless to say, the U.S. will have less flexibility to offer additional sanctions relief in the future once the Senate is under GOP control, and that could affect negotiations this year for the worse.