Wendy Davis says she is not running for U.S. Senate in 2020 and instead is considering a bid for the U.S. House.

"I'm looking very seriously at Congressional District 21," the former Democratic nominee for governor said in a new podcast released Friday, referring to the traditionally Republican district that Democrats came close to flipping last year.

Davis, also a former state senator, had mulled whether to take on U.S. Sen. John Cornyn, R-Texas. But in the podcast, "The Rabble: TX Politics for the Unruly Mob," Davis made clear she is no longer weighing a Senate campaign and reiterated her call for U.S. Rep. Joaquin Castro of San Antonio to enter the race.

"There's a reason I made a decision not to run for this Senate seat against John Cornyn," Davis said on the show, which was taped Thursday. "I've been very candid about the fact that my dear friend Joaquin Castro is someone that I'd like to see run."

In November, Republican Chip Roy narrowly won District 21 against Democrat Joseph Kopser, who came up 3 percentage points short. Kopser had been considering another run for the seat — or a Senate bid of his own — but recently announced he will not seek any office in 2020.

TX-21 is one of six GOP-held districts in Texas that national Democrats are now targeting for next year. It stretches from Austin to San Antonio and out to the Hill Country.

"Joseph Kopser gave a valiant effort [in 2018] — worked so, so hard and came very, very close," Davis said on the podcast. "Can we do it for 2020? I want to make sure that we have the ability to win it, and I believe we do. And, I want to believe I'm the right person to help us do that."