Why do backbenchers in parliament, particularly party rebels, speak more often during floor debates in some countries than they do in others? Sven-Oliver Proksch and Jonathan Slapin employ a comparative institutional approach to explain the link between electoral rules and debate participation, arguing that parliamentary debate is a forum that parties and their MPs exploit for electoral purposes—not to persuade other MPs to vote their way, but instead to communicate policy positions to other MPs and, most importantly, to communicate with voters. Testing their theory and the implications of a formal model, Proksch and Slapin make a compelling theoretical and empirical case that electoral rules shape who, and what, we hear on the floor of parliaments in advanced industrial democracies.

Parties use speeches to signal information about MPs’ policy positions to voters, directly and through the media. Proksch and Slapin theorize that in countries with electoral systems that incentivize parties to protect their brand name, party leaders will monitor and control their MPs’ floor speeches to ensure they send a unified message to the public. By contrast, in systems that incentivize MPs to cultivate a personal vote by creating a name for themselves, party leaders exercise less control over speaking time and speech content.

Proksch and Slapin present a formal model where floor speeches are the result of a delegation game played between party leaders and backbenchers. They collect an impressive array of data to test their hypotheses, including their own survey of parliamentary parties, a catalogue of parliamentary rules for lower chambers in 22 advanced industrial democracies, decades of member-level speeches in Germany and the United Kingdom, speeches during debates over fiscal stimuli in Germany and the United Kingdom, rules over the allocation of speaking time in the European Parliament, and MP speeches in New Zealand before and after changes in their electoral rules. The immense amount of data, and its variety, and the empirical rigor of their analysis go a long way toward reassuring any potential skeptic.

Some of Proksch and Slapin’s best evidence comes from their analysis of the relationship between electoral systems and parliamentary rules of procedure for lower chambers in 22 advanced industrialized democracies. They create three categories of parliamentary rules around speaking on the floor: rules that give members floor access and parties little control, rules that favor party leaders but still provide members with some speaking opportunities without leaders’ consent, and rules that give party leaders control over who speaks. They also classify countries’ electoral systems into three categories according to how much they incentivize personal vote seeking. They find a significant relationship; electoral systems that give members strong incentives to seek a personal vote are more likely to have rules limit that leaders’ control over members’ access. Relying on data from their own survey of parliamentary group administrators and party leaders in 25 advanced democracies, Proksch and Slapin also demonstrate that as parties become more heterogeneous and divisive, leadership monitoring in party-centered systems increases, while it decreases in systems with personal vote incentives. Strikingly, in most of the parties surveyed (92%), leaders require MPs to provide advance notice of a speech deviating from the party line and will monitor such speeches.

How do electoral systems and debate rules affect individual-level member behavior? Proksch and Slapin compare how often MPs speak on the floor in the German Bundestag between 1976 and 1998 and the United Kingdom House of Commons between 1979 and 2004. MPs have little reason to cultivate a personal vote in Germany’s mixed-member proportional closed-list electoral system compared with the UK’s single-member district plurality system, whereas party leaders in Germany have a much greater incentive to control the party message. They find that, as hypothesized, party leaders in Germany gave more speeches than backbenchers (especially those elected from districts rather than lists), whereas party leaders in the UK gave fewer speeches. Importantly, MPs who are ideologically distant from their party are more likely to deliver floor speeches in the United Kingdom and less likely to deliver floor speeches in Germany. The differences between Germany and the United Kingdom are consistent in analyses of members’ speeches on fiscal stimulus measures during the global financial crisis.

Proksch and Slapin take advantage of a 1996 rules change in New Zealand to analyze the same MPs serving under different electoral and parliamentary rules. When New Zealand moved from a plurality electoral system to party-centered proportional electoral system, party leaders gained control of parliamentary speaker lists. The 43 MPs from the Labour and National parties who served from 1991 to 1999 changed their behavior as Proksch and Slapin hypothesized, with rebellious backbenchers speaking more often during budget debates before 1996, when they had incentives to develop a personal vote and had more access to the floor.

Proksch and Slapin make significant contributions to the literature on comparative politics, political institutions, and legislative politics. The notion that electoral institutions incentivize political parties and their members is hardly new, but incorporating and analyzing party leaders’ control, or lack thereof, of their members’ participation in parliamentary debate is an important contribution to the literature.

Proksch and Slapin teach us a lot about parliamentary debate. Most scholars have overlooked the significance of legislative debate, perhaps over frustration that there is little evidence that it changes legislative outcomes. Proksch and Slapin, by contrast, conceptualize speech as a “tool for communication between MPs, parties, and the electorate” (p. 9). They show that speech is important with strong and convincing evidence supporting their argument that electoral systems affect party leaders’ control over their members’ access to the floor.

Important questions remain, however, about the nature and significance of speeches as a communication tool to reach voters and the specific mechanisms linking members’ speeches to voters. How often do MPs’ speeches reach the electorate, either directly or through the media, compared to other forms of communication that party leaders can’t control (though may monitor, as Proksch and Slapin note)? Party leaders must think speeches matter, if they carefully restrict and monitor them when it’s in their electoral interest to do so, but it is not clear how important speeches are in the broader electoral context. While speeches are indeed publically available, readers are left wondering the extent of their use by members or their opponents at election time, and whether they affect members’ electoral fate.

As legislative politics scholars increasingly recognize that the roll call record is not the only—and often not the best—indicator of legislative behavior or preference, Proksch and Slapin provide additional evidence that going beyond the roll call record is critical. In their analysis of intraparty dissent in the Labour Party over the reaction to the financial crisis in 2008 and 2009, they find that no Labour Party MPs dissented from their party in their votes, suggesting perfect party unity, but in fact 7.8 percent of MPs expressed disagreement in a floor speech or the media.

Proksch and Slapin’s analyses often obscure potentially important distinctions among backbenchers, the members who are lumped into one category defined by only the fact that they are not party leaders. Backbenchers thus include many types of members, including junior members, those MPs who aspire to party leadership and those who buck the party. At the member-level, Proksch and Slapin also analyze backbenchers’ distance from their party, showing they are more likely to speak when they need to attract their own votes. Yet, overall, it is not clear how often backbenchers are speaking out against their own party, speaking in praise of their own party, or simply touting their latest accomplishment, which may have nothing to do with the party brand. The type of backbencher in question—and the content of his or her speech—has implication for the relationship between leaders and their members.

Proksch and Slapin do not focus on debate in the U.S. House of Representatives, but changing dynamics in the House nonetheless raise interesting questions. They include the House in their coding and analysis of 22 lower chambers, and they may be too quick to conclude that in “… the United States, the party leadership has few incentives to intervene because there is little weight placed on party unity” (p. 53).

Even as members of the House have incentives to build a personal vote and use floor time to do so, party leaders in the United States put great weight on unity in today’s polarized and competitive era. Leaders have been increasingly likely to coordinate party messages during one-minute speeches (when the least gatekeeping on speechmaking is imposed) since the mid-1990s. And in special rules governing consideration of legislation, parties delegate control of speaking lists during debate on legislation to a floor manager of each party, but floor managers typically craft their lists strategically, often ensuring that speakers are consistent with the party’s message.

Even as Proksch and Slapin make a very compelling case that party leaders make strategic decisions about the allocation of their MPs’ floor speeches, readers will look forward to learning more—hopefully in future work by these authors—about the content of parliamentary speeches and the fate of the MPs who deliver them, both inside and outside of parliament.