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.

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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.”

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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.

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