Republicans are scrambling to save the seat of Senator Ted Cruz amid concerns he is not seen as “likeable” enough by voters and an onslaught from a charismatic, insurgent Democratic challenger.

While Mr Cruz, 47, is a favourite of the Tea Party wing of the Republican Party, he is widely disliked on Capitol Hill, by members of both parties. In 2013, he helped force a government shutdown in an effort to derail Barack Obama’s Affordable Care Act.

But now Republicans are rallying to try and help Mr Cruz, as polls show his seat in Texas – traditionally a solid red state – is at danger of being lost. Already worried about the prospect of losing control of the House of Representatives, Republicans are doing all they can to keep their narrow hold of the Senate. Some analysts believe that campaigning help from Donald Trump – who when a candidate in 2016 insulted Mr Cruz’s wife, referred to him as “Lyin’ Ted” and suggested his father was involved in the assassination of John F Kennedy – is the only thing that could save him.

“I don’t think there is any doubt that Ted Cruz is in for the fight of his life,” Jeanne Zaino, professor of political science at Iona College in New York, told The Independent.

“Texas is becoming a purple state but it is still red. Ted Cruz was runner-up to Trump in 2016. If he were to lose – and it’s still a big if – it would be a seismic shift. But if there was a year when there was a perfect storm in which he could lose, it is this year.”

Texas has long been a tough place for Democrats seeking national office.

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In 2016, Mr Trump carried Texas 52-43. While Ann Richards is celebrated as serving as a Democratic governor of Texas from 1991-95, the last senator from Texas was Bob Krueger, who was appointed to the seat by Ms Richards. He served just six months and lost his effort to win election to Republican Kay Bailey Hutchison. Mr Cruz was elected to the senate in 2012 in a 56-40 victory over his Democratic challenger.

But polls show his 2018 Democratic challenger Beto O’Rourke, is putting up a much sterner challenge. An average of polls collated by RealClearPolitics gives Mr Cruz a lead of just 4.5 per cent, while one poll published last month by Emerson scored it 39-38 in the incumbent’s favour – a statistical tie.

Mr O’Rourke has received widespread praise for his thoughtful and measured campaign. One video of him – in which he talked about his support for the so-called kneeling protests of American Football players such as Colin Kaepernick and others – went viral.

The Hill reported that Republicans were now pouring money into the seat to try and help Mr Cruz. It said the entire senate Republican leadership hosted a fundraiser for him at the end of June, and senate majority leader Mitch McConnell, whom Cruz once famously called a liar on the senate floor, has made the maximum donation to Mr Cruz’s campaign through his leadership PAC, the Bluegrass Committee.

Mr Trump has promised to go to Texas next month to campaign with Mr Cruz, someone he frequently used to mock and insult as a “pathological liar”.

“I will be doing a major rally for Senator Ted Cruz in October. I’m picking the biggest stadium in Texas we can find,” he recently tweeted.

“As you know, Ted has my complete and total endorsement. His opponent is a disaster for Texas – weak on Second Amendment, Crime, Borders, Military, and Vets!”

At the weekend, Rick Tyler, who served as Mr Cruz’s communications director during his 2016 presidential run, told MSNBC it was possible the candidate could lose.

“It’s possible – people say no, it’s not possible because again you look at Texas and say ‘it’s a red state and it’s never going to happen’ but Beto O’Rourke has consistently out-fundraised him two to one, and he doesn’t take PAC money,” Mr Tyler said.

Those comments followed the publication by The New York Times of a leaked audio recording of White House federal budget director Mick Mulvaney and Ronna McDaniel, the Republican National Committee chairwoman, discussing the midterm elections with donors and party officials.

“There’s a very real possibility we will win a race for senate in Florida and lose a race in Texas for senate, OK,” Mr Mulvaney said. “I don’t think it’s likely, but it’s a possibility. How likeable is a candidate? That still counts.”