O'Rourke, who has represented a House district based around El Paso since 2013, has wowed observers with his tireless grassroots organising, powerful and optimistic message, and Obama-like knack for raising money from small donors.
For these reasons, win or lose, he will vault into consideration for the 2020 presidential nomination as Democrats cast about for the ideal foil for Trump.
But even as the state's demography grows steadily more favourable for Democrats, Texas has been tantalising but ultimately disappointing them for years. And here we are again, allowing hope to overcome experience, asking if maybe, just maybe, 2018 is the year the Republican Party will finally lose its grip on the Lone Star State? Alas, probably not.
Despite fielding the best candidate in a generation up against one of the least likeable incumbents in recorded history, Texas seems set to dash Democratic hopes once again. An average of recent polls shows Ted Cruz with an eight-point lead over O'Rourke, suggesting the Democrat will barely outperform Hillary Clinton, who lost to Donald Trump by nine points in 2016.
I've worked on enough campaigns to know that anecdotes are no match for data, but it's hard to square those numbers with the evident energy and organisation around the O'Rourke campaign.
One Uber driver, an African immigrant, told me he's volunteering for the first time on a political campaign, disgusted by Trump, and inspired by O'Rourke's unifying message.
Swinging by Lockhart, Texas, famous for Black's BBQ and deep in Cruz country, I came across a Democratic field office, brimming with volunteers.
Even my Bush-voting buddy, who works in the oil industry no less, is giving O'Rourke a vote. "Republicans have too much power for their own good," he told me, "the White House, Congress, the Courts. We need to balance the scales."
This sentiment is reflected in national numbers, too, where Democrats are favoured over the GOP by close to double digits when it comes to which party should control Congress.
It's often been said it would take a "perfect storm" for any Democrat to win a statewide race in Texas and, while there's some hope in the menacing clouds overhead, perfection remains a tall order.
The biggest problem for O'Rourke is turnout, especially among the rapidly growing population of young Latino Texans, who routinely fail to show up at the polls.
Just 43 per cent of Hispanic voters in the 18-29 age group registered in 2016, and less than a third bothered to vote. Even after two divisive, racially charged years of Trump, only 49 per cent of Latinos nationwide express interest in taking part in November's election, compared to 61 per cent of Republican-inclined whites.
Absent a surge in Hispanic and millennial registration and turnout, O'Rourke is forced to compete for a voting electorate that is much older and whiter than the state itself. This allows Cruz to cast O'Rourke as a dangerous affront to "traditional Texas values", a line of attack that will keep working as long as only traditional Texas voters - white, older, conservative - turn up at the polls.
Unless and until Democrats work out how to translate favourable demographic changes into boosted turnout, they will continue to come up short.
• Shane Te Pou, a supporter of the Labour Party in New Zealand, has been attending US elections since 1994.
