Rep. Steve Stockman (R-Texas) is challenging Sen. John Cornyn (R-Texas), the No. 2-ranking GOP senator, in next year's Republican primary.

Stockman's late filing, which came just ahead of the deadline, sets up a battle between the conservative firebrand and Cornyn, who has a solid hold on the party establishment. The Texas battle will be one of at least seven Republican primaries, including challenges to longtime Sen. Thad Cochran (R-Miss.) and Senate Minority Leader Mitch McConnell.

Spencer Yeldell, a spokesman for the Texas Republican Party, told Business Insider that a little before 6 p.m. CT on Monday, Stockman withdrew his application for his current seat and filed to run for Senate.

Stockman personally announced his run in an interview with the far-right publication World Net Daily. He said he was challenging Cornyn because of how he "undermined Sen. Ted Cruz’s fight to stop Obamacare."

"And now, it looks like Cruz was right and Cornyn was wrong. He (Cornyn) sided with the president, essentially, in making sure Obamacare became law while Cruz did everything possible to stop it," Stockman said.

Cruz, of course, is the junior senator from Texas who has quickly become a conservative hero through his efforts to defund the Affordable Care Act in his first year as a senator. Sean Rushton, a spokesman for Cruz, told Business Insider that Cruz "will likely not get involved in any incumbent primaries."

A recent survey from Public Policy Polling found that Cornyn could be vulnerable to a legitimate conservative challenge next year. According to the poll, 49% said they would like a more conservative candidate than Cornyn, compared with 33% who said they supported Cornyn.