With a varied cast of characters pursuing each party’s nomination for president, the subject of electability — the idea that some candidates are inherently better or worse general election candidates than others — keeps coming up. It’s come up in reference to Bernie Sanders, a Vermont socialist in a party that has seen multiple northern liberals lose the presidency. It’s come up in reference to Hillary Clinton, who would be the first woman to top a major party ticket and whose political career has been dogged by scandals. And electability questions have been raised perhaps most often on the Republican side, about the two candidates now leading the GOP field, Donald Trump and Ted Cruz.

But what does “electability” mean? Is it real?

Oftentimes, it’s simply a stand-in term for ideology. When a pundit or analyst says a candidate is “not electable,” what they really mean is they’re too ideologically extreme for general election voters. There’s some evidence for this — for example, two of the most ideologically extreme candidates of the 20th century, Republican Barry Goldwater and Democrat George McGovern, each received far fewer votes than predicted by political science forecasting models based on non-ideological factors like the economy. And, of course, it’s intuitive that voters would be put off by candidates whose views lie far outside the mainstream.

These ideological tinged electability concerns are most often raised about Cruz and Sanders. Data suggests that both are, in fact, more extreme than past nominees. Looking at Sanders’ DW-NOMINATE Common Space scores (which places all House and Senate members on the same left-right scale), Sanders, as of the 113th Congress, was well to the left of any recent Democratic president with a Congressional voting score. He clocked in at -.523 (more negative is more liberal), compared with President Obama’s -.363, LBJ’s -.236, and JFK’s -.308. Walter Mondale, who was widely believed to be too liberal to have been elected president in 1984, had a score of -.447 in the last Senate in which he served. Hillary Clinton’s score was -.381.

So yes, Sanders stands out ideologically – but not as much as Cruz, with a score of .943.

CANDIDATE PARTY COMMON SPACE SCORE George McGovern Democrat -0.569 Bernie Sanders Democrat -0.523 Walter Mondale Democrat -0.447 Hubert Humphrey Democrat -0.404 Hillary Clinton Democrat -0.381 John Kerry Democrat -0.373 Barack Obama Democrat -0.363 John F. Kennedy Democrat -0.308 Lyndon Baines Johnson Democrat -0.236 Richard Nixon Republican 0.167 Bob Dole Republican 0.328 John McCain Republican 0.378 Barry Goldwater Republican 0.656 Ted Cruz Republican 0.943 The ideology of past nominees Source: VOTEVIEW

So Sanders and Cruz aren’t electable because they’re too extreme ideologically? Not so fast. Ideology is notoriously difficult to measure, and these scores certainly don’t capture everything or tell the full story. Moreover, members of Congress have become increasingly consistent in their party-line voting since the 1970s, and the electorate has become more partisan in its voting habits as well. With a substantial portion of the electorate committed to voting D or R in a general election, and with competitive elections that have clear policy stakes, candidates with more off-center ideologies may not make much of a difference.

Another factor worth considering is that recent elections — nearly all of them — have selected candidates, and presidents, who were not necessarily moderate but whose ideological identities were easier to obscure. Although there exist ways to measure the ideology of governors, for example, they don’t have the same kinds of voting records as legislators. And, as erstwhile presidential candidate Chris Christie was eager to tell us, governors have to run their states, so they often have to work across party lines, within their states and in partnership with the federal government.

Since Jimmy Carter was elected in 1976 as a racial liberal but moderate on many other issues, we’ve elected three more governors, a sitting vice president and a senator with a very brief record. They’ve featured varying types of ideological identities, but one possible argument is that the current era favors candidates who are ambiguous – who can nod to party ideals and still maneuver in an increasingly polarized system. It’s not clear whether Sanders or Cruz, who make no claims to centrism or unity (compared to say, candidate Obama in 2008), would fit this at all. But by rejecting the standard Democratic label, Sanders does bring a degree of ambiguity to the process.

Of course, the candidate who brings the deepest ideological ambivalence to the election is Trump. The Internet has been abuzz trying to figure out how to classify him for months, seeking historical comparisons, discussing the meaning of “fascism” and engaging critiques from other Republicans that he’s not conservative enough. Deeply conservative in some respects and ideologically elusive in others, Trump fits the ambiguity profile that is associated with a number of successful candidates. So maybe in that sense, Trump is “electable.”

But “electability” also often serves as a stand-in for more nebulous qualities, like the candidate’s personality and image. And Trump does more poorly by this meaning. When we think about a candidate’s appeal to voters, it’s tempting to look to favorability ratings to tell us what we want to know. (Trump, for example, has really bad favorability numbers.) But there are a couple of problems with this. First, early favorability ratings aren’t great predictors of who will win, suggesting that they don’t really capture a lot about electability at this stage in the game. (They do better at predicting who will win when we get closer to the election.) Second, favorability ratings just tell us that voters gravitate toward candidates that they like, so we’re basically saying “this candidate is likeable because voters like him.” This measure doesn’t tell us anything about why voters like certain candidates — about the traits and personal qualities that make someone electable.

So what about personal characteristics? Conventional wisdom suggests that candidate traits matter in a superficial way – that voters gravitate toward smooth speaking skills, elite education, height and looks.

But there’s a substantial body of political science research on how citizens perceive candidates’ personal characteristics. Much of the foundational research in this area comes from the 1980s and 1990s, when experts saw an age of “candidate-centered politics” emerging. During this time — which seems like a distant memory now — scholars and political analysts saw weakened parties and a rise in voting habits that disregarded party label in favor of candidates’ personal qualities and ability to connect directly with voters. These studies found that the kinds of qualities that were important to voters fell into consistent and substantive categories: integrity; competence and reliability; charisma – a category that includes items like “ability to inspire others”; and appearance and background. In a 1999 paper, political psychologist Carolyn Funk found that the perception and effect of candidate traits vary in ways that are difficult to explain, although “ratings of candidate traits tend to vary, on average, in ways that are consistent with ‘real’ differences among them.” However, later experimental research also suggests that perceptions of candidate qualities like charisma can also be driven by political conditions. In other words, voters care whether candidates appear intelligent, honest and inspiring – but the way this matters changes with context, and the qualities can be in the eye of the beholder.

What we can take from this research is that personality and personal characteristics matter. And they matter in a more substantive way than conventional wisdom usually suggests. But these are shaped by perception — and by media coverage and campaign dynamics — so it’s hard to say at the outset of a campaign whether a candidate’s personality is an asset or a liability.

If we want to suggest that a particular candidate is too liberal or too conservative to be competitive in a general election, then we should just say that. We don’t need a clunky label like “electability.” But what about the intangible “it” factor that draws crowds to rallies – what candidates like Martin O’Malley and Jeb Bush didn’t have, while surprise candidates Sanders and Trump appear to?

Empirical answers about what makes a candidate electable, likeable or trustworthy remain somewhat elusive. Voter perceptions are shaped by candidate qualities, but also by political context. This is frustrating for those who want solid answers. But it’s good news for those who want to support candidates who fall outside the usual boundaries in personal characteristics, temperament or ideology. Electability is a moving target.

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