With the Obama Administration having secured sufficient votes in the US Senate to ensure the nuclear deal with Iran stands, the toll of this bitterly fought contest can now be taken. During what has been a particularly bruising debate even by American political standards, it was by no means clear the agreement was going to survive efforts to have Congress repudiate it. 

Secretary of State John Kerry and former Senator Richard Lugar, 2 September. (Flickr/US State Department.)

Proponents argued that the deal was the best available option for preventing Iran's acquisition of nuclear weapons, and failure to approve it would favour Iran's nuclear and regional ambitions far more than any gaps in the agreement. Opponents argued that Iran cannot be trusted, that the deal is full of loopholes, and that Iran would translate the lifting of sanctions into greater regional power and support for terrorist groups. They portrayed the deal as a capitulation and the Obama Administration as weak on Iran. 

Israel's visceral opposition to the deal was another major factor galvanising congressional Republicans and putting pressure on a number of Democrats. Both sides were pushed to extremes in their denigration of the opposition; deal supporters were accused of inviting another Holocaust, and deal rejecters of holding common cause with anti-American Iranian hardliners

Republican opposition to a nuclear arms agreement negotiated by a Democratic president is nothing new. I witnessed this for myself when working in the office of then-US Republican Senator Richard Lugar in 2010, when he fought a grueling bipartisan battle alongside then-Senator John Kerry against fellow Senate Republicans to ratify the New START disarmament treaty with Russia. Lugar and Kerry succeeded, but only barely. 

The old adage that politics ends (or should end) at the water's edge was never completely true, but it nonetheless reflected the view of many in the political establishment that domestic politics should not significantly undermine the national interest, the international credibility of the state, or key alliances and relationships. Rejection of the Iran deal would likely have isolated the US, and left key negotiating partners high and dry, calling into question the diplomatic efficacy and good faith of the world’s superpower..

To debate in good faith what is or is not in the national interest in the domestic political arena is right and proper; to obstruct, deny and reject simply to deprive the other side a win is not. While there were important risks associated with the Iran deal that deserved to be raised, the political nature of much of the opposition is impossible to ignore. The intensity of the furor surrounding the deal, and the fact that the Administration's opponents came so close to blocking one of its key foreign policy initiatives, is cause to reflect on the extent to which partisan politics is limiting policy options in Washington — in particular, policy options that involve compromise.

As a statesman with a long history of working across the aisle on matters of foreign policy and international security, the now-former Senator Lugar is acutely familiar with the brutal reality of modern American politics. Lugar was ousted from the Senate by a Tea Party-backed Republican challenger who attacked, in part, his record of bipartisan cooperation. Almost five years after he and Kerry pushed the New START Treaty uphill through the Senate, I caught up with Lugar to ask whether he thought the political space for diplomacy in Washington has shrunk.

The Senator said he remains optimistic about the ability of the US Government to conduct rigorous foreign policy. Behind the scenes of the more controversial, media-saturated issues, Democrats and Republicans on legislative bodies such as the Senate Committee on Foreign Relations (on which Lugar served as Chair and Minority Leader on many occasions) still find sufficient common ground to avoid gridlock. But on politically charged issues such as the Iran deal, Lugar lamented the increasingly obstructionist political environment in Washington as a major challenge.

All of this is concerning, because it suggests partisanship in Washington could inhibit high-stakes diplomacy at a time when the US manages one of the most important and consequential security relationships in its modern history: that with a rising and more assertive China. 

Cyber attacks, island-building in the South China Sea, disputed territories, human rights and economic spill-over from China's slowdown are all issues likely to increase political attention on America's China policies, especially leading into the 2016 presidential election. While the Iran deal has taken up a lot of the foreign policy oxygen in the primary contests to date, the candidates have already made aggressive forays on China policy, and this is likely to increase over time.

The controversy over the Iran deal raises the spectre that as key points of contention with China become the subject of politicised debate in Congress and on the campaign trail, the ability of the executive to conduct deft diplomacy in response to tensions with China will be curtailed. In particular, an environment where acts of significant diplomatic compromise, concession or accommodation are portrayed as capitulation will make it increasingly difficult for US leaders to find creative ways to solve disputes and avoid escalation with China. Already the stagnant opposition to US ratification of the UN Convention on the Law of the Sea (UNCLOS) arguably weakens US credibility and limits policy options on territorial disputes and island-building in the South China Sea.

One does not need to subscribe to an 'accommodationist' school of thought on US policy towards China to at least acknowledge that diplomatic compromise is an option that the US needs to keep open as it manages growing Chinese ambitions in the region. The concern is that is getting harder and harder to make that case in Washington.