Joaquin Castro has a lot to lose. Beto O’Rourke has nothing to lose.

In a purely political sense, that’s the major difference between these two promising, third-term congressional Democrats. Both of them want Ted Cruz’s U.S. Senate seat, and O’Rourke will officially launch his campaign on Friday with an announcement in his home town of El Paso.

Castro is mulling his options and plans to make a decision by the end of April. Castro is cautious by nature, but even if he wasn’t, it would be understandable for him to hit the pause button before committing himself to a Senate campaign.

Even before O’Rourke came into the picture, this race, on the degree-of-difficulty scale, looked to be only slightly easier than trying to win the Olympic 100-meter hurdles in high heels. It’s not just that Texas Democrats have lost every U.S. Senate election since 1988. It’s that the defeats have been such brutal routs.

Every Democrat I’ve spoken to in recent weeks would classify themselves as a Castro fan, but most of them are vaguely glum at the thought of Castro running for the Senate next year. While they’d love to see a serious Democratic challenge to Cruz — a conservative Republican who finished second to Donald Trump in last year’s Republican presidential sweepstakes — they don’t believe Cruz can be beaten.

O’Rourke just makes the whole obstacle course more daunting. Castro would now have to fight for his party’s nomination against a smart, charismatic progressive, who is coming off the bipartisan PR coup of a live-streamed, 36-hour road trip with Republican Congressman Will Hurd.

Running for the Senate is no gamble for O’Rourke. He already had committed to term-limiting himself out of the House after four terms. So if O’Rourke had decided to stay put in 2018, that would have only meant two more years in the House for him. When it comes to evaluating his political future, he feels the self-imposed urgency of now.

For Castro, it’s different. He holds a coveted seat, a valuable piece of political real estate.

For one thing, District 20 is the only congressional district completely contained within the boundaries of Bexar County. As a result, Castro can uniquely claim that he is San Antonio’s congressional representative.

Also, District 20 is a solid Democratic seat, and once you’ve got it, it’s yours. Henry B. Gonzalez held it for 38 years, and Gonzalez’s son, Charlie, followed up with 14 years of his own. Over four decades, Henry B. had exactly one tough District 20 race: the first one, a 1961 special-election contest against Republican candidate John Goode Jr.

Gonzalez pulled out a close win over Goode, with the help of then Vice-President Lyndon Johnson and Mexican film star Cantinflas, both of whom made campaign stops at San Antonio supermarkets and shopping centers. A year later, Gonzalez was unopposed, and he never looked back.

To put it simply, the District 20 seat is a destination, not a way station. Even the possibility of court-mandated redistricting shouldn’t change that.

While no Texas Democrat would say this publicly, if Castro runs for the Senate, the party faces the demoralizing prospect of losing two of its brightest congressional lights in the same year. And Castro would lose a political platform (including a role on the House Intelligence Committee) that has made him a mainstay on CNN, MSNBC and ABC.

Of course, there’s more cachet in being one of 100 senators, rather than one of 435 representatives, and pulling off a statewide win over Cruz in this blood-red state would instantly vault Castro to the top echelon of American politics.

But any objective risk assessment would suggest that a 2018 Senate run is a bad bet.

The flip side of that assessment, and one that I’ve often made in this column, is that Texas Democrats will never get anywhere unless their most formidable figures are willing to put themselves out on the line, and risk losing in statewide races.

That issue came up four years ago when Joaquin’s twin brother Julián — then the mayor of San Antonio — resisted calls from fellow Democrats to run for governor. (Julián also has indicated that he won’t seek elective office next year.)

With O’Rourke in the Senate race, Democrats know that they have someone who will at least be able to push Cruz next year. If Castro jumps in, Democrats will worry that one of their favorite sons is pushing himself out of Congress.

ggarcia@express-news.net

Twitter: @gilgamesh470