Stockman told the conservative news site WND he would file his ballot application Monday evening, just before the deadline.
“We are extremely disappointed in the way [Cornyn] treated his fellow congressmen and broke the 11th commandment and undermined (Sen.) Ted Cruz’s fight to stop Obamacare," Stockman said Monday. "We think he needs to be held accountable for his decisions."
Cornyn, the Senate's second-ranking Republican, refused to join Cruz' failed attempt to defund Obamacare -- a crusade that led to October's federal government shutdown. Cornyn nevertheless opposes Obamacare.
Stockman, known for oddball antics, including inviting an Obama-impersonating clown to perform in a Texas rodeo and bringing fellow right-wing firebrand Ted Nugent as his guest to the 2013 White House Correspondents' Dinner, promised a "vigorous campaign."
“I don’t know that I can beat him, but I am sure going to try,” Stockman said. “In Texas, conservative policies win over stabbing fellow Republican in the back."
Brad Dayspring, a spokesman for the National Republican Senatorial Committee, came out strongly in support of Cornyn.
"John Cornyn is one of the most conservative Members in the Senate and strong leader for the state of Texas. We are proud to support Senator Cornyn, and while this primary challenge is quite the head-scratcher, it will be defeated," said Dayspring.
The Senate Conservatives Fund hasn't yet decided whether it will back the challenger: