FACTBOX - Texas and its presidential primary

(Reuters) - The Texas Democratic presidential primary on Tuesday is considered a must-win for Sen. Hillary Clinton's embattled campaign against rival Sen. Barack Obama.

Republican presidential front-runner Sen. John McCain has an almost insurmountable lead over his last major Republican rival, former Arkansas Gov. Mike Huckabee.

Voting ends in most of the state at 8 p.m. EST (1 a.m. British time on Wednesday), with a tiny portion at 9 p.m. EST.

Following are a few facts about Texas and its primary:

* Texas Democrats will send 228 delegates to the national convention, the biggest single bloc remaining. Of those, two-thirds are granted based on the popular vote in each of 31 state Senate districts, with districts that were more Democratic in the 2004 and 2006 elections getting more delegates. The other one-third are awarded based on the outcome of caucuses held after the polls close on Tuesday.

* The Lone Star State's economy, with a gross domestic product of $881 billion (444 billion pounds) in 2004, is larger than Indonesia's, the 16th biggest national economy in world. Only California and New York have bigger U.S. state economies. The leading industries in Texas are trade, real estate, and oil and gas. With a population of about 23.5 million people, Texas is the second most populous U.S. state after California.

* Clinton's hopes in Texas rest heavily on her ability to win overwhelming support from the state's Hispanic voters. There are an estimated 8.3 million Hispanics in Texas, second only to the estimated 12 million in California.

* Conservatives have dominated both political parties in Texas in recent years. The state political climate has been marked by a preference for low taxes and a relatively low level of state services, a generally anti-union work environment, culturally conservative social policy and limited environmental regulation.

* Texas ranks last in the country by percentage of residents with a high school diploma (78.3 percent) and total tax burden per capita ($1,368). It ranks first among states for executions since 2005 (19) and shopping malls built since 2004-2005 (112).

Sources: Texas Democrats; Texas State Library and Archives Commission; Census Bureau; "Texas Politics," the University of Texas at Austin; StateMaster.com

(Reporting by Mark Felsenthal, editing by Stacey Joyce)

(To read more about the U.S. political campaign, visit Reuters "Tales from the Trail: 2008" online at blogs.reuters.com/trail08/)