Missouri bellwether
The Missouri bellwether is a political phenomenon that notes that the state of Missouri has voted for the winner in every U.S. Presidential election beginning in 1904 except in 1956.  Missouri is also considered a bellwether of U.S. views on hot-button social issues such as stem cell research, school vouchers, and same-sex marriage. Some economists also consider the state a bellwether for economic trends such as consumer confidence and unemployment.

# Political history
Between 1960 and  2004, Missouri's popular vote was within about one and a half percent of the national popular vote margin. The lone exception was the Dwight Eisenhower landslide of 1956, when the state gave a 4,000-vote plurality  two-tenths of one percent  to neighboring Illinois Governor Adlai Stevenson. Missouri's 96% accuracy in voting with the national consensus includes the "too close to call" elections of 1948, 1960, 1976, and 2000. In recent election years, a Presidential debate has always been held at Washington University or the University of Missouri-St. Louis.
In 2006, Missouri's bellwether status gained renewed attention because of the 2006 Senate race between incumbent Republican Senator Jim Talent and Democratic State Auditor Claire McCaskill, which was considered vital to which party controls Congress. Additionally, Missouri had a ballot measure, Missouri Amendment Two, regarding stem cell research that drew national attention as an indicator of mainstream sentiment towards this controversial issue.  On Election Day 2006, both McCaskill and Amendement 2 received majority support among Missouri voters. McCaskill's victory as well as the victory of Sherrod Brown over Sen. Mike DeWine in Ohio and Jim Webb's defeat of Senator George Allen in Virginia were key to Democrats regaining power in the U.S. Senate. 

# Possible causes
The cause of Missouri's bellwether status is most often cited as its location and demographics. The Chicago Tribune calls Missouri the "bellwether state that almost exactly mirrors the demographic, economic and political makeup of the nation". A microcosm of the country's current political make up, Missouri has its two Blue "coasts" of St. Louis and Kansas City with Red middle and southern areas.
Since 1980 the mean center of U.S. population of the United States (which has been moving steadily westward) is in Missouri (currently in Phelps County). Missouri is in the center of the country, distant from the coast and the national borders. It shares a border with three Southern states, three Plains states, and two Midwestern states.
Missouri has a mixture of urban, suburban and rural populations.  In the state's two urban areas, St. Louis considers itself the furthest west of the eastern cities while Kansas City considers itself the furthest east of the western cities.
Missouri was a border state in the American Civil War and tried to remain neutral in the conflict.  It was a slave state and so was represented by a star on the Confederate flag but the state remained in the Union during the conflict.

# Continued bellwether status?
Whether Missouri will continue to be a bellwether remains to be seen.  One of the more important national phenomena that has not had the same impact in Missouri as in the rest of the country is the influx of immigrants, particularly Latinos. Analysts and journalists in recent times have pointed to states like Ohio, New Mexico, Pennsylvania and California as more accurate political and cultural bellwethers. As for Missouri, Slate columnist Chris Suellentrop has said that the state "isn't so much a bellwether as it is a weathervane: It doesn't swing the country, the country swings it..." and that Missouri is a better indicator of whether a trend is mainstream than of what the next new trend will be.