Sen. Hillary Rodham Clinton of New York has the overall lead in delegates to the Democratic convention, with 261, according to an Associated Press analysis of delegate totals. Sen. Barack Obama of Illinois has 196.
Obama has won more delegates in the primaries and caucuses held to date. But Clinton leads in endorsements from superdelegates - party and elected officials who automatically attend the convention and can support whomever they choose, regardless of the outcome of the primaries.
A total of 1,681 Democratic delegates in 22 states and American Samoa will be up for grabs Tuesday. However, it will be difficult for either candidate to take a decisive lead because the Democrats award delegates proportionally in every state. That means the second-place finisher in every state will also win delegates, as long as they get at least 15 percent of the vote.
A total of 2,025 delegates are needed to secure the Democratic nomination.
Sen. John McCain has an even narrower lead over former Massachusetts Gov. Mitt Romney in the race for delegates to the Republican convention. McCain has 102 delegates, including endorsements from party leaders who automatically attend the convention. Romney has 93 delegates and former Arkansas Gov. Mike Huckabee has 43, according to the AP analysis.
A total of 1,023 Republican delegates will be at stake in 21 states Tuesday.
The Republicans have a better chance of crowning a clear front-runner because nine Super Tuesday states award all their delegates to the candidate who wins the primary or caucus. Other Republican states award delegates based on vote totals in individual congressional districts.
A total of 1,191 delegates are needed to secure the Republican nomination.
The AP tracks the delegate races by projecting the number of national convention delegates won by candidates in each presidential primary or caucus, based on state and national party rules, and by interviewing unpledged delegates to obtain their preferences.
In some states, like Iowa and Nevada, local precinct caucuses are the first stage in the allocation process. The AP uses preferences expressed in those caucuses to project the number of national convention delegates each candidate will have when they are chosen at county, congressional district or state conventions.
