Texas Rep. Joaquin Castro has been at the forefront of the Democratic effort to overturn  President Donald Trump’s national emergency declaration to fund a wall along the southern border. 

Almost every Democrat and 13 Republicans supported Castro’s disapproval resolution, which passed Tuesday evening by a vote of 245—182. 

But while Castro has taken a leading role in his caucus’s push to rebuke Trump, he’s been less vocal about his Senate ambitions. 

“I’ll be glad to talk about that on another day,” he said with a laugh Tuesday when asked if he’s weighing a challenge to GOP Sen. John Cornyn.

That conversation could come sooner than he’d like. Former Democratic Rep. Beto O’Rourke, whose eye-popping fundraising and unconventional campaign style saw him nearly unseat Texas’ other Republican senator, Ted Cruz, last November, has said he will announce by the end of the month whether he’s running for president or taking on Cornyn.

Asked to confirm a Politico report that Castro would support another Senate bid by O’Rourke, or consider running himself if his former colleague runs for the White House, Castro said, “We’ll talk about it another time.”

He’s not the only Texas Democrat who could challenge Cornyn if O’Rourke does not. Former state Sen. Wendy Davis and onetime House hopeful MJ Hegar are also potential candidates. 

While O’Rourke’s decision looms, Castro’s central role in the disapproval resolution has brought him some national attention. Speaker Nancy Pelosi noted in a press conference Monday that Castro, who chairs the Congressional Hispanic Caucus, “has been working on this for a while and he made sure that we were ready.”

Also watch: First 2020 Senate race ratings are here

Fraternal ties

The four-term congressman has often been mentioned as a candidate for higher office. But it’s unclear whether he would launch a challenge to Cornyn while his twin brother, Julián, is running for president. 

The Castro brothers have never run for office in the same campaign cycle. Joaquin first ran for the Texas state House in 2002 and has since run in even-year elections, successfully winning a bid for the U.S. House in 2012. Julián has run in odd-year elections, first winning a race for San Antonio City Council in 2001, later running successfully for San Antonio mayor in 2009. He became secretary of Housing and Urban Development in 2014.

“They’re kind of a left-right combo,” said Texas Democratic consultant Colin Strother, who has advised both Castro brothers. “And for Joaquin to step aside from Julián’s presidential campaign and run for Senate would be breaking from their pattern that’s proven very successful.”

Of course, it remains to be seen how long Julián Castro’s presidential bid will last, especially in an increasingly crowded Democratic field. And Joaquin Castro could take his time to weigh a challenge to Cornyn if O’Rourke decides not to run — the 2020 election is still 20 months away. The filing deadline in Texas is Dec. 9, and candidates in competitive Senate races tend to launch their bids 12 to 16 months before Election Day.

Strother said Castro’s efforts with the disapproval resolution could raise his profile along the state’s border with Mexico, but he doubted it would be a major issue in the Senate race. Issues such as health care, the economy and infrastructure would be more likely to be top of mind for voters, Strother said. 

Manny Garcia, the executive director of the Texas Democratic Party, countered in a phone interview that the border wall issue will be part of broader argument that Cornyn put partisan politics first and backed Trump even when his policies hurt Texas.

“You don’t see John Cornyn actively fighting against [Trump],” Garcia said. “That’s just not Texas.”

The Lone Star State remains split on whether a wall at the southern border is necessary, but 60 percent of Texans surveyed in a Quinnipiac poll released Tuesday disapproved of Trump declaring a national emergency to fund the wall’s construction. 

A formidable incumbent

While Cornyn has expressed concerns about the precedent set by Trump’s move, he told reporters Tuesday he plans to oppose the disapproval resolution in the Senate. He has already been preparing for a competitive race, scoring an early endorsement from the president and building up his campaign war chest.

Cornyn ended 2018 with nearly $5.8 million in the bank. O’Rourke had $286,000 on hand after raising more than $80 million in the 2018 cycle. Castro, who represents a deep-blue district in San Antonio, had nearly $129,000 in his House campaign account, which could be used for a Senate race.

“Sen. Cornyn and the campaign will be ready for whoever decides to run for Senate whether it is billionaire Beto or Castro or Wendy Davis,” Cornyn campaign manager John Jackson wrote in an email. “Sen. Cornyn looks forward to contrasting his vision for Texas and that of the Democrats’ vision of open [borders] and job killing policies like the Green New Deal.”

Democrats see Texas as shifting in their direction, evidenced by O’Rourke’s competitive run last year — he lost to Cruz by 3 points — and victories further down the ballot. While Trump carried the state by 9 points in 2016, it was the smallest margin for a GOP presidential nominee in 20 years.

But Cornyn, a former state attorney general and Texas Supreme Court justice, will be tougher to beat than Cruz, as some Democrats acknowledge. Although O’Rourke came close, a Democrat hasn’t won a statewide race in Texas since 1994. Inside Elections with Nathan L. Gonzales rates the Senate race Solid Republican.

Still, Democrats expect to field a strong Senate challenger, though they know it could be a while before someone emerges.

“We have a long, storied history in Texas of waiting until the last minute to decide on U.S. Senate candidates,” Strother said. “I don’t see us breaking that tradition anytime soon.”