President Donald Trump endorsed Sen. Ted Cruz on Friday, promising to hold a big campaign rally for him in Texas.

“I will be doing a major rally for Senator Ted Cruz in October,” Trump wrote on Twitter. “I’m picking the biggest stadium in Texas we can find.”

Washington Republicans are terrified that Beto O’Rourke is gaining traction in Texas with the help of enormous support from liberal activists.

The latest NBC poll showed Cruz up by only four points in his re-election campaign.

Earlier in August, Cruz said he would be happy to have Trump visit Texas on his behalf.

“I would certainly welcome his support, and I hope to see him in Texas,” he said.

O’Rourke’s growing star power has attracted the attention of Hollywood celebrities and the media, building buzz for a possible 2020 run for president.

“Whether he wins or loses his race—and yes, even if he loses—O’Rourke should be included in every conversation about the 2020 Democratic primary,” Peter Hamby wrote for Vanity Fair, referring to “The Legend of Beto.”

Trump restated his endorsement of Cruz.

“As you know, Ted has my complete and total Endorsement,” he wrote. “His opponent is a disaster for Texas – weak on Second Amendment, Crime, Borders, Military, and Vets!”: