Come November, it’ll either be feast or famine for Beto O’Rourke’s political career — and, by extension, the Democratic Party in Texas.

O’Rourke, the El Paso congressman challenging Republican Sen. Ted Cruz, recently told Peggy Fikac, the Austin bureau chief for the San Antonio Express-News, that if he loses to Cruz, he won’t run again.

It’s easy to scoff at such a promise. After all, no candidate wants to create a sense that they’re just paving the road for a future campaign.

In the case of O’Rourke, however, it has the ring of truth.

For one thing, he voluntarily term-limited himself out of his U.S. House seat, promising that he would hold the seat for no more than four terms. Sure enough, three terms into his congressional career, he gave up his House seat to take on Cruz.

For another, as Fikac reported, O’Rourke, 45, is making an extreme personal sacrifice in his underdog bid for the Senate. He has three children, ranging in ages from 7 to 11, and his intense campaign schedule — which already has taken him to nearly every one of the state’s 254 counties — means his kids are growing up with dad on the road.

It’s a sacrifice he’s willing to make one time. It’s not likely that he would want to do it again, at least not in the near future.

If O’Rourke pulls off an upset in November, he will instantly become the biggest rock star in national Democratic politics, and the most important Texas Democrat since Lyndon Johnson.

If that sounds like hyperbole, try naming any contemporary Democrat, in any state, who has pulled off a victory with the degree of difficulty involved in O’Rourke’s Senate race. Breaking a 24-year winless streak in the second most populous state in the country, for a party whose biggest names — Bernie Sanders, Joe Biden and Elizabeth Warren — are either in or approaching their 70s, would be monumental.

But the impact goes beyond the statistical achievement.

O’Rourke, with his Kennedy-esque looks and defiantly idealistic exuberance, has that rare ability to inspire voters. In a nation filled with politicians who make voting sound like something you should do — in the way that you should eat your broccoli — O’Rourke makes his followers feel like voting is something they’re compelled to do — in the same way that I was compelled to listen to the new Janelle Monáe album 14 times the day it was released.

A November victory would mean that “O’Rourke” and “presidency” would start popping up in the same sentence even before he gets sworn in as a senator.

With the election six months away, O’Rourke already has attained an unusual degree of national celebrity for a representative from West Texas.

Former “Sex and the City” star Sarah Jessica Parker recently sported an O’Rourke campaign button at the Tribeca Film Festival. The hosts of Pod Save America often cite O’Rourke as the epitome of what Democratic politics should be right now. Rosie O’Donnell made the maximum allowable contribution to his campaign.

O’Rourke also sat for a 10-minute interview on the HBO show “Real Time with Bill Maher” and was profiled on this week’s edition of the Showtime political series, “The Circus.”

Of course, Cruz has framed all this attention as proof that the O’Rourke campaign is being driven by out-of-state elitists who don’t understand Texas values.

And that brings us to the political mountain O’Rourke must climb. While a recent Quinnipiac University poll had him only three points behind Cruz (47-44 percent), the numbers were likely skewed in O’Rourke’s favor by the fact that the poll sampled registered, rather than likely voters.

There’s also the fact that Democratic hopes for a blue-wave election seem shakier than they did even a few weeks ago. In a new CNN poll, Democrats hold just a three-point point lead over Republicans in a generic congressional vote, compared to a 16-point Democratic lead in late February.

With a thin Democratic ticket in Texas this year, O’Rourke won’t be able to depend on a blue wave — he’ll have to be his own blue wave.

If he loses (and if this really is a now-or-never election for him), the Texas Democratic Party will lose one of the most promising political talents it has produced over the last generation. His political career would be over, a couple of months after his 46th birthday.

That’s the way it goes in Texas. After all, former San Antonio Mayor Julián Castro, at the age of 43, is gearing up for a presidential run because, in a cost-benefit analysis, he determined that it makes more sense than running for statewide office.

Feast or famine. It’s a way of life for Texas Democrats.

@gilgamesh470

Gilbert Garcia is a San Antonio Express-News columnist. Read more of his stories here. | ggarcia@express-news.net | @gilgamesh470