Serving Texas for more than 30 years in the state House and Senate, Democrat Carl Parker says, even though Texas was blue, it was never a liberal state.

"It was a very divided party," Parker says. "We had what we call loyal Democrats and conservative Democrats."

Along with Democratic governors for 100 years -- from Richard Coke in 1874 to Dolph Briscoe, who left office in 1979 -- Texas voters picked Democratic presidential candidates in all but one election from 1948 until 1972. That's when they chose Richard Nixon.

"The last Democrat to win the presidential contest was Jimmy Carter in 1976," says Dr. J.P. Nelson, assistant professor of political science at Lamar University.

So what caused the shift in voters? Experts say the answer is two-fold.

The first issue is population growth. Between 1960 and 1980, the state grew from about 9.5 million people up to more than 14 million.

"Just like now, there were a lot of people moving from out of state," Nelson says.

"Texas had probably the greatest inflow of outsiders of any state in the union for a period of time," adds Parker.

Meantime, the values of the Democrat and Republican parties started shifting.

"What really put them over the top are cultural issues - abortion, gay rights and related causes - really becoming part of the national conversation in the '80s when they hadn't been in the '60s and '70s," Nelson says.

"The blue-collar Democrats, traditionally working in the plants and refineries, are fed up with it," says David Bradley, a Republican member of the State Board of Education. "That doesn't represent their values."

Looking back at the 1964 presidential election, 63 percent of texas voters went blue for Lyndon Johnson. In 2012, however, only 41 percent of Texans voted for Barack Obama. Parker blames some of those changes on Texas Dems losing touch with their constituents.

"Because the Democrats had the governor, lieutenant governor, speaker of the house, the majority of the senate and house, it got too easy to raise money," Parker says. "Democrats abandoned their grassroots contacts and ways of running campaigns."

Now in 2016, there's little doubt Donald Trump will get the majority of votes here, according to Nelson.

"It's just a matter of by how much?" he says, adding that Tuesday's results will likely affirm Texas' status as a red state for another election cycle.