Historical reenactors read the Declaration of Independence outside the National Archives on July 4, 2014, before the National Independence Day Parade in Washington. (Evelyn Hockstein for The Washington Post)

Any discussion of U.S. politics — whether in a newspaper, on TV or even on Facebook — quickly turns to our polarized political system. Perhaps somewhat surprisingly, many scholars argue that Americans are not very polarized on the issues, though some scholars do take the opposite position. But political scientists broadly agree that Democrats and Republicans increasingly dislike and distrust one another, a phenomenon known as affective polarization. For example, according to the Pew Research Center, roughly half of Americans hold very negative attitudes toward members of the other party, describing them with words like “closed-minded,” “dishonest” and “immoral.” Partisans also say that the other party makes them feel negative emotions like anger, fear and frustration, and more than 4 in 10 see the other party as a “threat to the nation’s well-being.”

Such attitudes have a number of pernicious consequences: They make governance more difficult, harm interpersonal relations and hamper economic exchange. Can anything be done to ameliorate such sentiments?

In an ongoing project, I investigate a number of different strategies for reducing this animus. In particular, in a recently published article, I found that drawing attention to American national identity softens that extreme dislike of the “other” party.

Why heightened American identity mitigates affective polarization

This approach draws on the common in-group identity model from psychology. Normally, when a Democrat thinks of Republicans, he or she thinks of them as a disliked political out-group. But seen from a different light, Democrats and Republicans are both part of a shared in-group: They are both Americans. If we remind people of their sense of American identity, then they should be able to see those from the other party as fellow Americans, rather than as rival partisans.

Using a series of experiments, I find strong evidence of this phenomenon. When I heighten subjects’ sense of American national identity by having them read an article about the United States’ strengths and asking them to reflect on what they like best about the nation, they rated the other party more positively on a number of dimensions. For example, they feel more warmly toward the other party, and think that positive adjectives, such as open-minded or generous, better describe them, while negative adjectives — like hypocritical or selfish — are less apt.

This happens in the real world. Around the Fourth of July — when Americans’ celebrations of our country strengthen our sense of national identity — affective polarization also tends to be lower. That said, these effects fade within a week or two, as the memory of the holiday wanes and politics returns to normal.

Will Trump’s Fourth of July speech mitigate polarization?

Presidents have long invoked this sort of national identity when they appeal to the public. Thomas Jefferson reminded us in his inaugural address that “we are all Federalists, we are all Republicans,” and Ronald Reagan asked us to unite not as partisans but as Americans in common cause. Perhaps no recent president invoked this sort of rhetoric more than Barack Obama, who frequently called for us to come together as one nation. Take, for example, this remark after the 2013 government shutdown: “We come from different parties, but we are Americans first. … Our regard for [the American people] compels us all, Democrats and Republicans, to cooperate, and compromise, and act in the best interests of our nation — one nation, under God, indivisible, with liberty and justice for all.”

Could President Trump’s address help bridge the divide between Democrats and Republicans? That would be extremely unlikely, for several reasons. First, Trump’s rhetoric tends much more toward the inflammatory rather than the conciliatory. If this speech follows that trend, it will do little to bring Americans together. Further, if the speech is expressly political, that’s how it will be interpreted. A speech about Trump and his accomplishments — rather than one that simply celebrates the nation — will be seen as part of his reelection campaign, cheered by his supporters and jeered by his opponents.

Presidential rhetoric in an era of partisan polarization has limits. It can be hard to look past the political angle of any speech or tweet, and so any such appeals are likely to have a minimal impact. Yet this does not mean we should completely despair for overcoming partisan polarization.

Small efforts — like people reaching across the aisle to genuinely listen to those with whom they disagree, or just seeing members of the other party as fellow Americans of good faith, rather than the enemy — can still bring us closer to bridging the divide among Americans and realizing the ideals expressed by the Founding Fathers.

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Matthew Levendusky is professor of political science (and, by courtesy, in the Annenberg School for Communication) and distinguished fellow in the Institutions of Democracy at the Annenberg Public Policy Center at the University of Pennsylvania.