The “rally around the flag” effect is when there’s a short-term surge in voter approval as the nation unites behind its leader during a crisis or emergency situation.
Political scientist John Mueller described the phenomenon in a 1970 landmark paper called “Presidential Popularity from Truman to Johnson.” Mueller defined it as arising from an event with three qualities: it’s international, it involved the country as a whole and it’s specific and dramatic.
One of the most prominent examples of the effect is when President George W. Bush saw a 39% increase in his approval rating — from 51% to 90 — following the September 11, 2001 terrorist attacks.
Other examples include President Jimmy Carter’s approval jumping 26 percentage points following the initial seizure of the U.S. embassy in Iran in 1979 and President George H.W. Bush receiving a 30 percentage point bounce following the success of Operation Dessert Storm in 1991.
More recently, the effect has been less pronounced. President Barack Obama received a six-point bounce following the mission to kill Osama bin Laden and President Donald Trump saw a slight bump in approval after the global outbreak of the coronavirus in 2020.