Blue wall (United States)
The blue wall is a term coined in 2009 in the political culture of the United States to refer to the 18 states (along with Washington, D.C.) that consistently voted blue (i.e., for the Democratic Party) in the six consecutive presidential elections from 1992 to 2012. This trend suggested a fundamental dominance in presidential politics for the Democratic Party. Conversely, the terms red wall and red sea are less-commonly used to refer to states that Republicans consistently won in the same time frame. States which have not voted consistently for one party are called purple, or swing states.
During the 2016 presidential election, Democratic nominee Hillary Clinton was considered a heavy favorite to win the electoral college because of this trend, but Republican nominee Donald Trump challenged the strength of the "blue wall" Rust Belt states of Michigan, Pennsylvania, and Wisconsin, which became swing states in the next three elections. The Trump victories in 2016 and 2024 included narrowly flipping these three states, while in 2020, Democratic nominee Joe Biden won the presidency by narrowly carrying all three states with lower than three percent margins.
The Southern United States had previously voted Democratic so reliably that it had been termed the "Solid South" until Republicans implemented the Southern strategy. The last Democratic presidential candidate to win a majority of Southern states was Jimmy Carter in 1976.