Since Mueller's original theories, two schools of thought have emerged to explain the causes of the effect. The first, "The Patriotism School of Thought" holds that in times of crisis, the American public sees the President as the embodiment of national unity. The second, "The Opinion Leadership School" believes that the rally emerges from a lack of criticism from members of the opposition party, most often in the United States Congress. If opposition party members appear to support the president, the media has no conflict to report, thus it appears to the public that all is well with the performance of the president. The two theories have both been criticized, but it is generally accepted that the Patriotism School of thought is better to explain causes of rallies, while the Opinion Leadership School of thought is better to explain duration of rallies. It is also believed that the lower the presidential approval rating before the crisis, the larger the increase will be in terms of percentage points because it leaves the president more room for improvement. For example, Franklin D. Roosevelt only had a 12% increase in approval from 72% to 84% following the Attack on Pearl Harbor, whereas George W. Bush had a 39% increase from 51% to 90% following the September 11 attacks.
Another theory about the cause of the effect is believed to be embedded in the US Constitution. Unlike in other countries, the constitution makes the President both head of government and head of state. Because of this, the president receives a temporary boost in popularity because his Head of State role gives him symbolic importance to the American people. However, as time goes on his duties as Head of Government require partisan decisions that polarize opposition parties and diminish popularity. This theory falls in line more with the Opinion Leadership School.
Due to the highly statistical nature of presidential polls, University of Alabama political scientist John O'Neal has approached the study of rally 'round the flag using mathematics. O'Neal has postulated that the Opinion Leadership School is the more accurate of the two using mathematical equations. These equations are based on quantified factors such as the number of headlines from The New York Times about the crisis, the presence of bipartisan support or hostility, and prior popularity of the president.
Political Scientist from The University of California Los Angeles, Matthew A. Baum found that the source of a rally 'round the flag effect is from independents and members of the opposition party shifting their support behind the President after the rallying effect. Baum also found that when the country is more divided or in a worse economic state then the rally effect is larger. This is because more people who are against the president before the rallying event switch to support him afterwards. When the country is divided before the rallying event there is a higher potential increase in support for the President after the rallying event.
In a study by Political Scientist Terrence L. Chapman and Dan Reiter, rallies in Presidential approval ratings were found to be bigger when there was U.N. Security Council supported Militarized interstate disputes (MIDs). Having U.N. Security Council support was found to increase the rally effect in presidential approval by 8 to 9 points compared to when there was not U.N. Security Council support.
According to a 2019 study of ten countries in the period 1990–2014, there is evidence of a rally-around-the-flag effect early on in an intervention with military casualties (in at least the first year) but voters begin to punish the governing parties after 4.5 years. A 2021 study found weak effects for the rally-around-the-flag effect.
A 2022 study applies the same logic of rally effects to crisis termination instead of just onset. Using all available public presidential polling and crisis data from 1953 to 2016, the researchers found that a president received a three point increase to their approval rating, on average, when terminating an international crisis. They suggest that the surge in approvals is as much related to a proof of a president's foreign affairs competency, as it is related to a mutual camaraderie in defense of the nation
. Additionally, the suggestion that a president can achieve approval boosts via ending conflict instead of initiating conflict makes less cynical assumptions about the options within a president's toolkit and provide an additional avenue for inquiry into diversionary war theories.
The effect has been examined within the context of nearly every major foreign policy crisis since World War II. Some notable examples:
Cuban Missile Crisis: According to Gallup polls, President John F. Kennedy's approval rating in early October 1962 was at 61%. By November, after the crisis had passed, Kennedy's approval rose to 74%. The spike in approval peaked in December 1962 at 76%. Kennedy's approval rating slowly decreased again until it reached the pre-crisis level of 61% in June 1963.
Iran hostage crisis: According to Gallup polls, President Jimmy Carter quickly gained 26 percentage points, jumping from 32 to 58% approval following the initial seizure of the U.S. embassy in Tehran in November 1979. However, Carter's handling of the crisis caused popular support to decrease, and by November 1980 Carter had returned to his pre-crisis approval rating.
Operation Desert Storm (Persian Gulf War): According to Gallup polls, President George H. W. Bush was rated at 59% approval in January 1991, but following the success of Operation Desert Storm, Bush enjoyed a peak 89% approval rating in February 1991. From there, Bush's approval rating slowly decreased, reaching the pre-crisis level of 61% in October 1991.
Following the September 11 attacks in 2001, President George W. Bush received an unprecedented increase in his approval rating. On September 10, Bush had a Gallup Poll rating of 51%. By September 15, his approval rate had increased by 34 percentage points to 85%. Just a week later, Bush was at 90%, the highest presidential approval rating ever. Over a year after the attacks occurred, Bush still received higher approval than he did before 9/11 (68% in November 2002). Both the size and duration of Bush's popularity after 9/11 are believed to be the largest of any post-crisis boost. Many people believe that this popularity gave Bush a mandate and eventually the political leverage to begin the War in Iraq.
Death of Osama bin Laden: According to Gallup polls, President Barack Obama received a 6% jump in his Presidential approving ratings, jumping from 46% in the three days before the mission (April 29 – May 1) to a 52% in the 3 days after the mission (May 2–4). The rally effect did not last long, as Obama's approval ratings were back down to 46% by June 30.
During World War I, most belligerents saw a lessening of partisanship. Most socialist parties abandoned their pledges to oppose wars and endorsed their governments, leading to the break-up of the Second International.
The incumbent Conservative Party's popularity spiked in the weeks following the COVID-19 outbreak in the United Kingdom.
The outbreak of the COVID-19 pandemic in 2020 briefly resulted in popularity spikes for several world leaders. President Donald Trump's approval rating saw a slight increase during the outbreak in early 2020. In addition to Trump, other heads of government in Europe also gained in popularity. French President Emmanuel Macron, Italian Prime Minister Giuseppe Conte, Dutch Prime Minister Mark Rutte, and British Prime Minister Boris Johnson became "very popular" in the weeks following the pandemic hitting their respective nations. Johnson, in particular, who "became seriously ill himself" from COVID-19, led his government to "the most popular in decades." It was uncertain how long their increase in the approval polls would last, but former NATO secretary general George Robertson opined, "People do rally around, but it evaporates fast."
There are fears that the president will misuse the rally 'round the flag effect. These fears come from the "diversionary theory of war" in which the President creates an international crisis in order to distract from domestic affairs and to increase their approval ratings through a rally 'round the flag effect. The fear associated with this theory is that a President can create international crises to avoid dealing with serious domestic issues or to increase their approval rating when it begins to drop.
^Curran, Margaret Ann; Schubert, James N.; Stewart, Patrick A. (2002). "A Defining Presidential Moment: 9/11 and the Rally Effect". Political Psychology. 23 (3): 559–583. doi:10.1111/0162-895X.00298. JSTOR3792592.