Recent efforts to explain the use of military force have focused extensively on political opposition leaders confront at home. If leaders prefer to stay in power, and most seemingly do, then domestic and foreign policy successes as well as a demonstrated ability to lead offer a narrative that will likely be attractive to domestic audiences. Yet, a leader's ability to achieve policy successes, at least in democratic states, remains conditional on legislative support. Indeed, in the U.S. context, congressional opposition to a president's policy agenda affects whether the public views a president as being a competent and effective leader. And, of course, the perception of these characteristics can influence a leader's longevity.
Presidents must nurture their relationships with members of the House and Senate if they hope to accomplish their policy and political goals. A president's reelection, reputation, and historical legacy are closely tied to his capacity for getting policy initiatives through Congress. Signature pieces of legislation, such as the 1964 Civil Rights Act or the Affordable Care Act, form perceptions of a president in the minds of voters and members of Congress. But, compared to the duration of typical legislative terms, presidents' window for policy movement is brief so they instinctively rush to establish a record of policy success. Legislative victories certainly can cement a place in history for presidents, but importantly they also demonstrate political leadership and signal political effectiveness, which can bolster a president's influence in Congress.
Still, constitutional imprecision as well as political and institutional advantages offer presidents greater unilateral authority in international affairs. The role of commander in chief as well as a need to speak diplomatically with only one voice enable presidents the ability to act in foreign affairs without congressional support. Such unilateral power is particularly valuable when Congress opposes and actively resists the domestic policy initiatives of a president. A president can then shift attention away from domestic legislative priorities to critical security concerns occurring overseas to demonstrate leadership and build political capital for the future. President Obama's actions on the Syrian crisis may serve as a case and point. Indeed, Representative Peter King made such a claim suggesting the White House leaked that President Obama signed a secret order to provide support (nonlethal) to the Syrian rebels. Interviewed on Fox News, Representative King forcefully asserted, "The only thing I can think of is this is an attempt to rehabilitate the president going into an election year to show that he's a tough guy" (Ovadia 2012). (1) Further, U.S. Special Forces operations, such as the one that nabbed Abu Anas al-Liby in October 2013, offered Obama an opportunity to shift media attention away from the government shutdown and debt-ceiling talks with Republicans to his own handling of national security.
Our analysis empirically assesses the relationship between the president's capacity to demonstrate political leadership through his support in Congress and his propensity to turn unilaterally to foreign policy. Similar to those who advocate the party cover view, we find that the president does consider the costs/constraints from a recalcitrant Congress in understanding presidential foreign policy decisions. In an era of intense partisanship and polarization, the president's party control of Congress conditions the propensity and level of political risks/costs executives face in their foreign policy endeavors. However, despite Congress possessing a common set of ex post tools to counter a president's unilateralism, we find important distinctions between presidential decisions in humanitarian actions versus the military use of force. This result adds an important dimension to the party cover argument and supports the contention of policy availability. Presidents are driven to demonstrate political leadership. And our findings show the president's relationship with Congress shapes executive incentives to engage in foreign policy leadership ventures and presidents value such opportunities differently across humanitarian and use-of-force decisions.
Specifically, we find that as presidents are able to pass greater numbers of important legislation, the likelihood they turn to humanitarian interventions decreases significantly. Because humanitarian actions tend to have lower political costs, executives are more willing to go it alone when their legislative leadership in Congress is faltering. Further, our evidence shows that as the president's legislative productivity increases, presidents are considerably more likely to engage in higher-risk military interventions. Military expeditions have far greater potential for significant political costs and so a strong relationship with Congress can defend/deflect executive actions from opposition voices. In this way, party control of Congress structures the level of political costs presidents face in making decisions about humanitarian or military ventures. When presidents are demonstrating legislative leadership with Congress, there is little incentive to turn toward humanitarian opportunities. But when legislative leadership in Congress is in short supply, the lower-cost humanitarian efforts become much more attractive targets as compared to military ventures. When presidents show strong legislative leadership in Congress, the costly hurdles to military adventures are more readily overcome.
This article proceeds as follows. First, we review extant literature on political accountability and leader decision making. We develop a theoretical discussion recognizing the importance of party cover and how such domestic structural conditions can shape presidential relations with Congress and presidential calculations for political leadership in foreign policy. We then specify models of foreign policy decision making to illuminate claims made by policy availability. Next we describe our data and research methods used to test the relationship between a president and Congress. Finally, we document our statistical model results and offer suggestions for future research.
Understanding the Politics of the Use of Force
Theoretical models of international politics and processes increasingly accept the premise that political leaders make foreign policy decisions with an eye on electoral fortunes at home (Bueno de Mesquita et al. 2003). Such an assumption has actually grounded diversionary theory from its inception (Enterline 2010). Indeed, popular culture and political science scholarship regularly conclude that policy choices, even foreign policy ones, primarily serve the political interests of elected leaders.
U.S. presidents enjoy substantial advantages over Congress in their capacity to influence foreign affairs more so than in the domestic policy realm. The constitutional ambiguity of the commander in chief as well as profound asymmetries in institutional resources and information allows the president great discretion to act unilaterally. In fact, Hinckley argues that "[t]he use of force shows the clearest conventional pattern: presidents are active and Congress accedes to what the president requests" (1994, 80). In the short run, Congress is poorly suited to stop executive-initiated foreign ventures in their tracks (Howell and Pevehouse 2005). Yet, the burgeoning literature shows that use of force decisions are shaped in important ways by changes in domestic politics and interinstitutional constraints.
Diversionary arguments suggest that domestic political and economic conditions trigger presidential incentives to act in foreign affairs. A well-timed display of military force can shift attention from an underperforming economic engine and rally support behind a leader and the soldiers and sailors he commands. Despite the intuitive appeal of diversionary theory (Levy 1989) and the qualitative case-study evidence that appears to support the basic premise, (2) large-N studies linking economic weakness or political unrest to the use of military force produce few if any robust empirical relationships. It is not that coefficient values are statistically insignificant (although in many studies they are; e.g., DeRouen 1995; Meernik and Waterman 1996; James and Hristoulas 1994), but that the findings fluctuate widely depending on data and modeling choices (e.g., compare Ostrom and Job  to Meernik and Waterman  and Brule, Marshall, and Prins ).
Scholars have also noted several conceptual problems with implicit assumptions in the diversionary model. Importantly, it remains unclear whether leaders actually benefit politically from any type of military operation. Not only does the iconic rally effect rarely materialize (Russett 1990; Lian and Oneal 1993) but also evidence suggests there is a consistent electoral cost to militarized conflict. Williams, Brule, and Koch (2010), for example, find no electoral benefit to incumbent leaders in nine Western democratic countries when using military force abroad. In fact, the use of force results in net losses to an executive's co-partisans in the legislature when the economy is doing poorly and provides no electoral benefit when the economy is strong. Moreover, diversionary theory demands that presidents be able to readily manipulate public opinion in foreign affairs, but empirical research suggests such opinion movement is not easily shaped by political elites (Jentleson and Britton 1998; Edwards 2003). Such evidence challenges diversionary theory. Voters are not diverted by a crisis overseas but rather remain concerned about salient problems at home.
Diversionary theory's singular focus on militarized conflict remains problematic as well. Kisangani and Pickering (2007b), for example, distinguish between benevolent and belligerent military interventions....