How Does the Texas Primary Work?
Texas has an open primary system, and voters do not register by party. An individual can vote in either, but not both, primaries. For example, even if a person voted in the 2006 Republican Primary, they can vote in the 2008 Democratic Primary.

Texas will send a total of 228 delegates to the Democratic National Convention. 126 delegates will be assigned based on primary results in 31 State Senate Districts (instead of allocating delegates by its 32 Congressional Districts like many states). The number of delegates in each Senate district varies based on previous Democratic turnout in the last two general elections. The delegates from each Senate District are assigned to candidates proportionally based on the percentages they receive on primary day.

Of the remaining 102 delegates, 67 are determined through a convention process that begins at precinct conventions (caucuses) on the night of March 4 and culminates with delegate allocation based on each candidate's delegate strength at the State Convention on June 6-8. Of those 67 delegates, 42 are "at large" rank and file delegates and 25 are pledged party leaders, legislators, and local elected officials.

The remaining 35 delegates are "unpledged" delegates, including 32 so-called "superdelegates" who are DNC Members, Members of Congress, a former House Speaker and a former DNC Chair. Three other delegate slots are reserved for highly-honored state Democrats, such as respected former officeholders.

• 126 Senatorial District Level Delegates allocated by primary results.
• 42 At-Large Delegates and 25 Pledged Party Leaders, Democratic Mayors and Legislators, all allocated by the presidential preference of delegates attending the State convention (with a 15 percent threshold).
• 32 Super Delegates made up of Members of Congress, Members of the DNC, past House Speakers and former DNC Chairs.
• 3 Unpledged Delegates (Add-Ons) elected through a three-tier, post-primary convention process. 

(Source: Texas Democratic Delegate Selection Plan)