Presidential nominee Hillary Clinton reacts as balloons and confetti fall on the final day of the Democratic National Convention in Philadelphia. (Carolyn Kaster/AP)

The Republican and Democratic conventions offered sharply contrasting visions of America and its challenges. As many observers noted, Democrats put forward an optimistic vision based on shared purpose and togetherness, with slogans like “love trumps hate” and “stronger together.” Republicans focused on threats like urban crime, terrorism and economic uncertainty, with slogans such as “make America safe again.” The Republicans depicted the United States as an embattled Gotham City while the Democrats described a shining city on a hill. Washington Post reporters Karen Tumulty and Robert Costa noted that this is a distinct reversal. In the past, each party has offered the other point of view.

Do U.S. voters prefer optimism or pessimism from their political leaders? An optimistic candidate may hope to attract voters to a rosy vision, but citizens may interpret that as naivete. Meanwhile, a pessimistic candidate may try to appeal to voters by presenting himself as a hard-nosed realist, promising to shelter them from the world’s terrors, but citizens may prefer a more bright  and upbeat tone. Which strategy is more effective is far from obvious.

We studied this question and the political implications of the two opposing strategies in a Journal of Politics paper published in 2014. Our research suggests that despite its potential drawbacks, Americans are more likely to reward a communication strategy based on optimism.

Here’s how we studied this, and what we found

As part of this study, we conducted a nationally representative survey administered by YouGov/Polimetrix online in 2010 to 1,500 American adults. We asked people on a seven-point scale: “Generally speaking, how optimistic or pessimistic do you want political leaders in the United States to be?” We also asked them to rate their own optimism.

Our respondents rate themselves as slightly optimistic (4.5), but want leaders more optimistic than themselves (5.3). This pattern is remarkably consistent, holding true across gender, political ideology, political party, religiosity and education. Notably, even though Democrats in our sample (4.8) were more optimistic than Republicans (4.3), both groups preferred optimistic leaders by roughly the same amount (5.3-5.4).

We also asked people to rank which traits they believed to be most important for political leaders to possess: “optimistic,” “pessimistic,” “overly optimistic,” “overly pessimistic,” “cautious,” “courageous,” “intelligent,” “daring,” “charismatic” and “reliable.” On average, optimism was ranked highly as a preferred trait among leaders (average rank: 2.2), only exceeded by reliability (1.4) and intelligence (1.5). The two least valued traits were “pessimistic” and “overly pessimistic.” Americans even preferred their leaders to be “overly optimistic” than “pessimistic.”

The news media and Americans share perceptions of politicians’ optimism

Respondents’ assessments of the optimism of their political leaders closely match how the news media depict them. We asked people to rate the optimism of eight recent presidential candidates. In a content analysis of major newspapers and magazines, we also coded how often the media noted the candidate as optimistic, normalized by how often that the politician was mentioned giving a speech.

As shown in the figure below, there is a strong correlation between how the media and the public view politicians. The most electorally successful politicians in recent memory — Bill Clinton and Ronald Reagan — were seen by both the public and the media as being particularly optimistic. In contrast, less-successful politicians such as Al Gore and John McCain were viewed as pessimistic. Of course, people may retrospectively evaluate winners as more optimistic. We therefore turn to experimental evidence.

We ran an experiment in which we provided American adults with vignettes of politicians setting optimistic vs. pessimistic expectations and also informed people about the eventual outcomes. Below is an example vignette in which we varied the information in brackets:

In a televised speech to the nation several years ago, a prime minister of a foreign country predicted that his country’s economy would [pick up/slow down] the following year. [Indeed, in line with that prediction/However, in contrast to that prediction], in the

12 months that followed that speech the country’s economy performed very [well/poorly] on every major economic indicator.

In many studies and iterations of this experimental design, we assessed attitudes toward optimism and pessimism about many policy areas that included the local economy, the global economy, national security and the environment. We also investigated areas where politicians sometimes offer optimistic forecasts about things that they don’t control, like sports events and the weather.

We find that when outcomes are good, our respondents rated politicians who were optimistic to begin with 25 to 50 percent higher on numerous dimensions (e.g., leadership, judgment, favorability) than politicians who were pessimistic but reality turned out better than expectations. That’s also true when politicians are talking about matters generally out of their control (9-28 percent).

In other words, Americans see optimism as a positive part of their politicians’ personalities, just as suggested by the evidence above.

U.S. voters like optimistic political leaders

This helps explain why, traditionally, presidential candidates have offered optimistic visions of the country’s future, from FDR’s 1932 campaign song “Happy Days Are Here Again” to Ronald Reagan’s 1984 “Morning in America” campaign commercial to Bill Clinton’s 1992 use of Fleetwood Mac’s “Don’t Stop.”

Donald Trump’s strikingly different tone in his convention address is a real gamble. Even Richard Nixon’s 1968 campaign, which Trump’s effort is often compared, was about “bringing us together” despite social strife. The tone of the Republican convention even contrasted with the “Make American Great Again” slogan, which could be seen as optimistic.

The two parties’ strikingly different tones are especially noteworthy, given their difference from the traditional points of view of liberals and conservatives. Conservatives in the Edmund Burke tradition generally stress the positives of the status quo as reasons to resist change. Liberals in the Thomas Paine tradition generally point out society’s deficiencies and stress the need for change.

Trump’s campaign is widely described as non-traditional. His doom-and-gloom speech is yet another moment of Trump defying historical precedent. Our research suggests that this strategy is likely to work against him.

Neil Malhotra is professor of political economy at Stanford University.

Yotam Margalit is associate professor of political science at Tel Aviv University.