After Mitt Romney’s announcement that he would not pursue the 2016 presidential nomination, attention has turned to the significance of Romney’s departure. The debate among political scientists has focused on whether Friday’s announcement means that Romney had lost an “invisible primary.”

There’s also been some discussion about how the decision affects the rest of the field. News outlets have focused on which candidates will benefit from Romney’s absence from the field – Bush, Walker, Christie, etc. But for political scientists, whose interests go beyond the individual personalities in the 2016 race, a different set of questions has emerged. Does a Romney-free field open up space for other candidates to enter the race? Or does his decision to drop out reflect an effective process of elite-driven winnowing, demonstrating to would-be candidates that the party has limited patience for trial balloons?

The answer to this depends on at least two things. First, there’s the extent to which party elites can control the early stages of the process. The Party Decides makes a strong case that elites influence the ultimate outcome of the race. But how much control do they exert over who enters or stays in the race, a year before any high school gyms fill with caucus-goers or any primary ballots are cast? In our piece on informal institutions, Jenny Smith and I found some evidence that party elites enforce norms about candidates dropping out later in the process, but exercising control over who runs in the beginning would be harder to justify.

Nevertheless, it doesn’t take a huge imaginative leap to hypothesize that party elites – especially those most concerned with the party “brand” – might wish to narrow the field early on. A couple of questions remain. For one, what kinds of carrots and sticks do elites have to offer presidential hopefuls in order to get them to leave the race? Is the main tactic to deprive the non-preferred candidate of funds and attention? Or do more direct tools exist?

The other question is whether there are two distinct groups of Republican candidates. In other words, another fairly mainstream candidate like Christie might see Romney’s absence from the race as an invitation to jump in. But do candidates like Rand Paul and Ted Cruz perceive Romney’s presence in the race as relevant to their political projects and ambitions? The answer might be yes – it’s the same party, after all. But it could also be no – they aren’t going after quite the same constituents within the party, and have distinct ideas about what Republican Party politics means.

There are far more questions than answers here. It’s hard to predict whether Romney’s decision to leave the race represents the beginning of process to narrow the field, or opens up space for other aspirants to fill. There’s a lot we don’t know about the causal mechanisms of the invisible primary. As a result, it’s difficult to predict the impact of a well-known candidate like Romney leaving the race. One way that political scientists might address these kinds of questions is to look at the “field” of candidates at different points as a dependent variable (as in this 2002 piece by Wayne Steger, John Hickman, and Ken Yohn; see this piece also) – adapting their method (or one like it) to count the number of effective candidates in different years and at different points in the campaign might be helpful for testing some of the elusive invisible primary mechanisms. Of course, we’d also need good ideas about the observable implications of those mechanisms.

From a substantive perspective, there’s also a chance that the two competing hypotheses are both true. If Romney’s decision not to pursue the nomination represented a signal that elites were ready to narrow the choices in the race, it’s possible that not all candidates received or heeded the signal. This would actually suggest that the Republican Party has two simultaneous, but distinct processes of nomination happening at once.

There might be one group of candidates who are responsive to incentives: the perception that they might lose if they stayed in the race, the belief that having a crowded field might hurt the party’s image or chances in the general election (doubtful, but commonly held wisdom), or the belief that staying in the race could cost support down the line.

But there’s nothing to guarantee that all or even most of the candidates in the race will do that. As I’ve written here before, insurgent politics appears to follow a different logic. And candidates who join the race in order to get publicity or to push an ideological agenda are less likely to respond to electoral and party incentives. Both parties have had some of these candidates in recent years (for the Democrats, think Mike Gravel in 2008 or Dennis Kucinich in 2004). Among Republicans, there are a couple of candidates whose chances at the nomination are probably slim, but who nevertheless have big enough political followings to make some difference in how the race unfolds.

The question at the heart of the elite winnowing issue and the debate over the invisible primary is really about how much control party elites have over the process. Elites have a strong incentive to shape the field of candidates before the primaries and caucuses begin. The evidence suggests that they have considerable capacity to do that – although that capacity may be limited. The other question is whether it’s limited to the establishment faction of the party.

[Cross-posted at Mischiefs of Faction]

Julia Azari

Julia Azari is an Assistant Professor at Marquette University.