HOUSTON (Reuters) - Texas was supposed to be a bastion of support for Hillary Clinton in the battle for the U.S. Democratic presidential nomination, but it may turn out to be her Alamo.

Her wide lead in Lone Star state polls has disappeared, and experts say it is looking more and more like her last stand against Barack Obama.

In one of history’s most famous battles, Texas independence fighters tried to stop the Mexican army at the Alamo in 1836, but they were wiped out by a larger force that overwhelmed them.

In this case, it is not soldiers, but Obama’s momentum, threatening to do the same thing to Clinton’s presidential aspirations.

After winning 11 straight contests, Obama, an Illinois senator, has overtaken Clinton in the Texas polls, erasing a double-digit lead she held a month ago.

A Reuters/C-SPAN/Houston Chronicle poll released on Saturday showed Obama leading 45 percent to 43 percent. The survey had a margin of error of 4 percentage points.

Texas and Ohio will vote on Tuesday in must-win primaries for Clinton, a New York senator.

“It is Hillary’s last stand and increasingly looks like it won’t be successful,” said Matthew Wilson, political scientist at Southern Methodist University in Dallas.

“At this point, Obama can do no wrong. He’s on an incredible ride and the air hasn’t started coming out of his balloon yet.”

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Texas, next door to former President Bill Clinton’s home state of Arkansas, was supposed to be Clinton country.

The Clintons forged strong ties to Texas Democrats while working in the state during the 1972 presidential campaign of George McGovern and had historic ties to black and Hispanic voters.

But Obama, according to recent polls, has taken big bites out of the Clinton coalition by splitting the white vote and winning sweeping support from black voters.

HISPANIC VOTES

Clinton is pinning her hopes largely on a big Hispanic vote in her favor.

Hispanics, by some estimates, make up about 20 percent or more of registered voters in Texas, compared to 12 percent for blacks and 66 percent for whites.

A Texas A&M University poll conducted February 18-24, showed Hispanics favoring Clinton over Obama 62 percent to 22 percent.

But a more recent Reuters/C-SPAN/Houston Chronicle poll, conducted Tuesday through Thursday, found Clinton’s edge among Hispanics had dropped to 55 percent, versus 33 percent for Obama.

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Texas A&M political scientist Sylvia Manzano said Obama has gained Hispanic support because he has had two weeks since the last primaries to campaign in Texas.

“What we’ve seen in the rest of the country is that the longer he has in a state, the more support he gets,” Manzano said.

Obama got help in strongly Hispanic south Texas last week from U.S. Sen. Edward Kennedy of Massachusetts, who sang a song in fractured Spanish at a rally in Laredo.

But the Clinton family, including daughter Chelsea, is working hard to shore up Hispanic support.

“There was a Clinton in south Texas every day last week,” Manzano said.

A record turnout is expected throughout the state, where long lines have marked early voting. Armed police officers will be stationed at polling places in San Antonio because such big crowds are expected.

With John McCain well ahead in the race for the Republican presidential nomination, and because Texans can vote in either party’s primary, Republicans have been voting in the Democratic race, University of Houston political scientist Richard Murray said.

Most are voting for Obama because they want to keep Clinton out of the White House, he said.

“We’ve always had our quota, plus some, of Hillary haters. T hey think they can drive a stake through her presidential heart, and they are hammering away with gusto,” Murray said.