One of the hot topics in national security circles has been whether President Obama would veto one, or both defense bills slated to reach his desk in the next few months. The odds changed dramatically with this week’s announcement of the Iranian nuclear deal. The fight it will touch off between Obama and Congress makes a presidential veto of one or both defense bills far less likely. 

To see how the Iran deal alters the veto calculus for the White House and perhaps for Senate Democrats, let’s examine the scenarios for both the National Defense Authorization Act (NDAA) and the defense appropriations bill. 

{mosads}The NDAA establishes the annual budget and policies for the Defense Department. The House passed its version in May; the Senate passed its version in June. Both bills received large, bipartisan majorities. Conferees are working out the differences between the bills, and a final version is expected to reach the President’s desk within the next few weeks. However, the White House has threatened to veto the measure if it increases defense spending above the Budget Control Act (BCA) cap, while leaving non-defense spending subject to the caps.  

Despite the veto threat, almost half of the Democratic caucus in the Senate joined their Republican colleagues in voting for the final NDAA. Clearly, this bill is important on both sides of the aisle.  

The question now is whether Obama will follow through on his threat, particularly as he is trying to convince many of these same Senate Democrats to support the Iran deal. Will Senate Democrats want to vote, in quick succession, to support a veto of a key defense bill and a widely panned deal with Iran? Obama appears to care more about getting the Iran agreement, so he might forego vetoing the NDAA if it improves his odds of getting the deal approved. 

While the NDAA is in the home stretch, the defense appropriations bill is stuck in the Senate. The appropriations bill, which provides the actual money for the Defense Department to spend, passed the House in June, winning bipartisan support despite another veto threat. However, Democrats have blocked action in the Senate with a filibuster threat. Senate Majority Leader Mitch McConnell (R-Ky.) has indicated that he may force repeated votes on the bill, in an attempt to increase political pressure on the Democrats.  

In September, as the end of the fiscal year draws near, the Senate will either need to finish work on the defense appropriations bill or pass some form of temporary funding for defense. Votes on the Iran deal, including a potential veto override, will likely happen in September as well.  

With so much public attention focused on national security, it may be exceedingly difficult for Senate Democrats to sustain their filibuster on defense appropriations. And while the White House clearly does not want to increase defense spending without proportional increases in domestic spending, having this debate overlap with the Iran nuclear debate will leave the Administration in a much tougher spot.  

Between now and the end of September, Congress and Obama have a full plate of national security issues. While the White House has threatened to veto the defense authorization and appropriations bills, the prospect of having them hit the president’s desk in the middle of the Iran debate poses a political problem for the president.  

The NDAA, because it is primarily a policy bill, may avoid a veto due to the Iran debate. The defense appropriations bill may escape a filibuster for the same reason. The White House and Senate Democrats will want to appear strong and credible on national security for the Iran debate. Voting against or vetoing defense bills will not help their case.

Johnson is the senior analyst for defense budgeting policy in The Heritage Foundation’s Allison Center for National Security and Foreign Policy.