The Democratic and Republican primaries in Texas are March 4. The Clinton-Obama tussle for national convention delegates is extremely tight, especially after Obama's victories Saturday in Nebraska, Washington and Louisiana.
The last time the Texas Democratic convention delegation was at stake in the midst of a national fight was 1988. Michael Dukakis won the statewide primary that year but virtually split delegates evenly with Jesse Jackson because of the state's unique Democratic nominating process.
Here's a short version of the party rules, which are 11 pages long.
A total of 126 delegates will be awarded based on the outcome of the vote in each of the 31 state senatorial districts.
But the number of delegates available in each district is not equal: Delegates are allocated based on the votes cast in districts in the 2004 and 2006 presidential and gubernatorial elections.
In the heavily urban, black districts of state Sens. Rodney Ellis of Houston and Royce West of Dallas, a good voter turnout in the past two elections means a combined total of 13 delegates are at stake in the two districts on Election Day.
Obama nationally has been winning eight out of 10 back voters, according to network exit polls.
But in the heavily Hispanic districts of state Sens. Juan Hinojosa of McAllen and Eddie Lucio Jr. of Brownsville, election turnout was low, and a combined total of seven delegates are at stake.
Clinton has been taking six of 10 Hispanic votes nationally. So a big South Texas win might not mean as much for Clinton as a big win for Obama in the two black districts.
In 1988, Dukakis won the statewide primary with 33 percent of the vote, followed by Jackson at 25 percent. Al Gore had 20 percent and Richard Gephardt had 14 percent.
But despite Dukakis' clear plurality victory, he split the state's delegates almost evenly. Dukakis took 72 delegates, Jackson 67. Forty-four were uncommitted.
"In '88, Jesse Jackson paid attention to the caucus process and had grass-roots organizers," said Garry Mauro, a former state land commissioner and Hillary Clinton supporter. "Dukakis did not pay attention to the caucus process."
The state's Republican primary is not nearly as complicated. If the GOP race is still alive between Sen. John McCain, the front-runner, and former Arkansas Gov. Mike Huckabee when the primary arrives, they will find an equal number of nominating delegates available in each of the state's 32 congressional districts