Key Primary States

• The New Hampshire primary traditionally kicks off the presidential campaign.Stockbyte/Stockbyte/Getty Images
  
  Even before the formal start of the presidential campaign, the Republican and Democratic parties conduct primaries to help determine their candidates for president and vice president. Early political polls in states that usually play a key role in primaries---such as New Hampshire, whose state law requires it holds the first primary in the nation---are therefore of great national significance. The clout such states attain has led to controversy as other states jockey for strategic position in the primary calendar.
  
  

Bellwether States

• Bellwether states most accurately and consistently reflect national electoral trends. While not as strategically as important as swing states, bellwether states attract a good deal of national polling for their predictive qualities. For a time Missouri was seen as the most consistent bellwether state. Until 2008 it had, from the beginning of the 20th century, supported the winning candidate in every presidential election except one. Some now view Iowa as a more accurate bellwether, with Ohio and Nevada mentioned as well.
  
  

Swing States

• A handful of states holds the key.FPG/Retrofile/Getty Images
  
  Swing states, sometimes called battleground states, are where the election is closely contested. The most important swing states are those which also carry a significant number of electoral votes. These states attract an enormous amount of polling attention, not to mention political advertising dollars. In the 21st century, Florida and Ohio have emerged as the heavyweight swing states. Even states with relatively few electoral votes can become critical swing states in a given election. This is especially true as the electoral map has become "locked in," with, for example, only three states changing their electoral color between 2000 and 2004.
  
  

Trend States

• Trend states may not be as significant as bellwether or swing states, but may nonetheless be important polling states because of the way they indicate long-term political and social trends. Most often mentioned in this vein is California. Despite holding 55 electoral votes, substantially more than any other state, it has tilted consistently Democratic in presidential elections and has thus not been the site of intense campaigning by the candidates. But California remains an important indicator of demographic trends, for example the rise of the Latino population, and social trends like the increasing importance of environmental issues.