The Primary Season: 2008 Democratic Calendar To become the Democratic nominee for president, a candidate needs to capture a majority of the 4,040 delegate votes. State primaries and caucuses select 3,248 “pledged” delegates, who are obligated to vote for the candidate their state chose. An additional 792 “unpledged” delegates — consisting mostly of party leaders and elected officials — are free to vote for any candidate. States are listed according to the first major event in its selection process; with several states still jockeying for early positions, some dates may change.
http://politics.nytimes.com/election-guide/2008/primaries/democraticprimaries/index.htmlThe Primary Season: 2008 Republican CalendarTo become the Republican nominee for president, a candidate needs to capture a majority of the 2,345 delegate votes. States are listed according to the first major event in its selection process; with several states still jockeying for early positions, some dates may change. Daily delegate totals reflect all delegates allotted to the state, even though some may not pledge their vote until a later date.
http://politics.nytimes.com/election-guide/2008/primaries/republicanprimaries/index.html