AUSTIN (CBSDFW.COM/AP) — Democratic Rep. Joaquin Castro of Texas is acknowledging that he will “seriously consider” running for U.S. Senate in 2020 against Republican John Cornyn.

His campaign on Friday confirmed Castro’s interest a day after his twin brother, Democratic presidential candidate Julian Castro, told The Associated Press his sibling is mulling a challenge against Cornyn.

Rep. Joaquin Castro (D-TX) speaks during a news conference about the resolution he has sponsored to terminate President Donald Trump’s emergency declaration February 25, 2019 in Washington, D.C. (credit: Chip Somodevilla/Getty Images)

Joaquin Castro, a former San Antonio mayor and housing chief during the President Barack Obama administration, didn’t give a timeline for a decision. He’s chairman of the Congressional Hispanic Caucus and sponsored the House measure passed this week that would block President Donald Trump’s national emergency declaration for a U.S.-Mexico border wall. Castro called Trump’s move “constitutional vandalism.”

No clear rival has yet emerged to challenge Cornyn in Texas. Democrat Beto O’Rourke narrowly lost his Senate race in Texas last year but says he will announce a decision soon on whether to run for president in 2020.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)