Bernie Sanders has claimed he can win the Democratic primary in Texas and then go on to defeat Donald Trump in the historically Republican stronghold in November.

On the back of wins in Iowa, New Hampshire, and Nevada, the Vermont senator has held rallies in the cities of El Paso, Austin, Houston and San Antonio.

“We have won the popular vote in Iowa, we won the New Hampshire primary, we won the Nevada caucus, and don’t tell anybody because these folks get very, very agitated and nervous,” he said in Houston. “We’re gonna win here in Texas, and in November we’re gonna defeat Trump here in Texas.”

The confidence of the Sanders’ campaign comes as his rivals have stepped up their attacks on him, arguing he is too left wing to beat Mr Trump in a general election.

At the party’s 10th primary debate on Tuesday in South Carolina, the Vermont senator came under fire for everything from his healthcare plan, to a trip to Moscow shortly after he got married, and comments made many years ago praising the results secured by Fidel Castro’s education system.

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“I think teaching people to read and write is a good thing,” Mr Sanders later told CNN. “That is a fact. End of discussion.”

Supporters of the Vermont senator, a self-described democratic socialist for more than 40 years, point to polls putting him ahead in next Tuesday’s Texas primary, one of more than a dozen states that will be voting on what has come to be known as Super Tuesday. An average of polls collated by RealClearPolitics puts him on 22 points, ahead of Joe Biden, 20, and Elizabeth Warren on 15 points.

Meanwhile, another poll, conducted for the Texas Lyceum, a non-profit group, suggested Mr Sanders was the strongest Democrat in hypothetical match-ups with Mr Trump, falling just three points short of him on 50-47. This compared to 51-46 for Mr Biden, 52-44 for Ms Warren and 51-43 for Pete Buttigieg.

A victory in Texas next Tuesday would mark a major milestone and potential tipping point for the Sanders’ campaign, as it seeks to collect delegates and tie up the nomination ahead of the party’s summer convention.

Yet a win in November would be little short of staggering. Texas is a major prize, with the highest number of electoral college votes, 38, other than California, where Mr Sanders also looks strong.

For more than a century, Texas was a Democratic stronghold but since the 1970s it has become solidly Republican. The last Democrat to hold a statewide office was in the 1990s, and the party’s last presidential candidate to win here was Jimmy Carter in 1976.

Demographic changes in places such as Houston have given Democrats cause to hope. The 2018 midterms saw the party pick up a handful of seats in the House of Representatives, and Beto O’Rourke’s long-shot challenge to Ted Cruz in the Senate race shocked both parties, even though Mr Cruz held on 51-48.

Last year saw at least six Republicans from the House announce they were standing down, amid a so-called “Texodus”. Among them was Will Hurd, the only African American Republican congressman.

The Independent previously reported on efforts to turn red Texas blue, driven in large part by large numbers of women candidates challenging for House seats, Senate races, and control of the state assembly, something considered a priority.

Yet longtime Texan political strategists from both parties believe while Mr Sanders could win the primary, it would very difficult to beat Mr Trump there.

Matt Mackowiak, president of the Potomac Strategy Group, told The Independent: “I think Bernie could win the primary. But if he’s the candidate in November, I think Trump will increase the nine point advantage he had in 2016.”

He added: “I think Bernie Sanders will be radioactive in the suburbs, and that he will also impact down ticket races.”

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Matt Angle, a Democratic strategist and founder of the Lone Star Project, a political action committee that funds Texas candidates, said last year that he believes the party could win the state if it had the correct candidate and was willing to spend up tp $100m on political advertising. He said the best candidates would be Mr Biden or Texan Beto O’Rourke, who has since dropped out.

Mr Angle said this week his assessment had not changed, and that he believed it would be hard for the likes of Mr Sanders or Ms Warren to win in Texas.

“I think Bernie Sanders has a ceiling in Texas,” he said. “I’ve been doing Texas politics a long time and I’ve seen how you win here, and how you lose. You don’t win by thinking you’re suddenly going to have this mass of new voters.”

He added: “We have been plagued by people from outside of Texas, coming here and telling us how to win, even though they have never ran a campaign here.”

Yet Mr Sanders appeared unconcerned.

“This is the most consequential election in the modern history or our country. We are not only going to win in Texas on Super Tuesday, we are going to beat ‘em in November. We are not going to have Trump for another term,” he told supporters at the Vic Mathias Shores park in Austin.

According to the Statesman, he added: “The pundits tell us Texas is conservative state. I don’t believe that for a minute.

“And I believe that if the working people of Texas, black and white and Latino, Native American, Asian American stand up and come out to vote, you’re gonna make this one of the most progressive states in America.”