Frequently Asked Questions
Common questions about U.S. election data and voting history
Learn about swing counties, bellwethers, margin calculations, and more. This FAQ covers the terminology and concepts used in U.S. election analysis.
What is a swing county?
A swing county is a county that changes which party it supports between elections. For example, a county that voted for Biden in 2020 but Trump in 2024 would be considered a swing county. The term can also refer to counties with close margins that could go either way. In 2024, most swing was toward Republicans, particularly in Hispanic-majority areas.
What is a bellwether county?
A bellwether county is a county that has historically voted for the winning presidential candidate. These counties are seen as barometers of national sentiment. Famous bellwethers include Vigo County, Indiana and Valencia County, New Mexico. However, many traditional bellwethers broke their streak in 2020 or 2024 as partisan polarization increased.
What does D+5 or R+10 mean?
D+5 means the Democratic candidate won by 5 percentage points. R+10 means the Republican candidate won by 10 percentage points. The margin is calculated as (Democratic % - Republican %). A positive number indicates a Democratic win, negative indicates Republican. For example, if a candidate gets 55% to 45%, that's a 10-point margin.
What is the difference between popular vote and electoral college?
The popular vote is the total number of votes cast nationwide. The Electoral College is the system that actually elects the president, where each state gets electoral votes based on its congressional representation. A candidate needs 270 electoral votes to win. A candidate can win the electoral college while losing the popular vote, as happened in 2000 and 2016.
How many counties are in the United States?
There are 3,143 counties or county-equivalents in the United States. This includes parishes in Louisiana, boroughs in Alaska, and independent cities in Virginia. Some states like Texas have over 250 counties, while Delaware has only 3.
What is a flipped county?
A flipped county is one where the winning party changed from one election to the next. For example, if County X went for Biden in 2020 but Trump in 2024, it "flipped" to Republican. In 2024, significantly more counties flipped to Republican than to Democrat, driven largely by shifts in Hispanic-majority areas.
What are the swing states in 2024?
The main swing states (also called battleground states) in 2024 were Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania, and Wisconsin. These states had close margins in recent elections and were heavily contested. All seven went for Trump in 2024 after Biden won Arizona, Georgia, Michigan, Nevada, Pennsylvania, and Wisconsin in 2020.
Where does your election data come from?
Our data comes from official state election returns, the Federal Election Commission, state Secretaries of State offices, and county election boards. For demographic data, we use the U.S. Census Bureau's American Community Survey. All data is verified against multiple sources for accuracy.
How do you calculate swing?
Swing is calculated as the change in margin between two elections. If a county was D+5 in 2020 and R+3 in 2024, the swing would be R+8 (moving 8 points toward Republicans). Positive swing indicates movement toward Democrats, negative indicates movement toward Republicans.
What is a pivot county or Obama-Trump county?
Pivot counties (also called Obama-Trump counties) are counties that voted for Barack Obama in 2008 and/or 2012, then flipped to Donald Trump in 2016 or later. These counties are often working-class, predominantly white areas in the Midwest and Northeast that shifted from the Democratic coalition. Many continued to vote Republican in 2020 and 2024.