U.S. Rep. Joaquin Castro "seriously" considering run against U.S. Sen. John Cornyn

WASHINGTON – U.S. Rep. Joaquin Castro's camp released a statement early Friday morning making clear that the San Antonio Democrat is mulling whether to forgo re-election next year and instead challenge U.S. Sen. John Cornyn, two days after Beto O'Rourke made clear he won't be vying for the seat.

"Congressman Castro will seriously consider running for Senate in 2020," Castro spokesman Matthew Jones emailed. "Right now, he's focused on protecting Texans — and all Americans — from the most consequential challenge to our constitutional separation of powers that we have seen in a generation.

"He will not stand by while the President attempts to unilaterally strip Texans of their land to build a wall in a manner that most Americans, especially Texans, disagree with."

Earlier this week, Castro was the lead House Democrat on a major pushback against President Donald Trump's emergency border wall order. The resolution, which Castro authored, passed out of the chamber and looks increasingly likely to pass the U.S. Senate. But Trump is expected to veto it, and it is unlikely that Democrats would be able to muster enough Republican support to override that veto.

Friday's Castro signal comes two days after the Tribune and other outlets reported that O'Rourke, a former Democratic congressman from El Paso, will pass on his own Senate run and is postured to run for president. Castro's brother, former Housing and Urban Development Secretary Julián Castro, is also seeking the 2020 Democratic presidential nomination.

Several other Democrats have not ruled out runs against Cornyn in 2020, including former state Sen. Wendy Davis and veteran M.J. Hegar.