This post has been corrected and updated. 

The anti-tax Club For Growth said Tuesday it doesn't plan to meddle in the Texas Republican Senate primary, even as Rep. Steve Stockman (R-Tex.) launched a surprise last-minute campaign against Senate Minority Whip John Cornyn (R-Tex.), who other tea party groups are eager to defeat.

Sen. John Cornyn (AP Photo/J. Scott Applewhite) Sen. John Cornyn (AP Photo/J. Scott Applewhite)

“While Congressman Stockman has a pro-economic growth record, so does Senator Cornyn, as witnessed by his 87% lifetime Club for Growth score,” said Club for Growth President Chris Chocola in a statement. "Our PAC evaluates three factors when looking at races that involve incumbents: 1) the strength of the incumbent’s record; 2) the degree of difference between the incumbent and the challenger on economic issues; and 3) the viability of the challenger. None of those factors weigh against Senator Cornyn, so we do not expect to be involved in the Texas Senate race."

Stockman is a far-right conservative with a penchant for stoking controversy with his remarks and tweets. He will begin his campaign against Cornyn as an underdog ahead of the March primary. Five other lesser-known Republicans are also in the race.

The Club for Growth's position contrasts with other national tea party groups, which left the door open to backing Stockman.

"We haven't decided yet whether we will endorse Steve Stockman, but we're glad he's running," said Matt Hoskins, the executive director of the Senate Conservatives Fund. "Texas deserves two conservative fighters in the Senate, not just one. John Cornyn has voted to increase the debt, raise taxes, bail out Wall Street banks, and fund Obamacare. He's part of the problem in Washington and voters deserve a choice."

The Madison Project echoed the two "fighters" line, a reference to Sen. Ted Cruz (R-Tex.), the conservative darling who refused to back Cornyn and is staying neutral.

"As Minority Whip, Senator John Cornyn's main job is to unite 41 votes against liberal legislation," said Madison Project Policy Director Daniel Horowitz. "On issue after issue, Cornyn has failed to whip votes against the Democrats, effectively handing Senator Harry Reid a supermajority.  Texans are starving for two fighters, and news of a primary challenger is quite welcome. The Madison Project hasn't met with any challengers yet, but we are hopeful that someone will emerge as a viable and consistent conservative alternative."

10: 20 am Correction: This post initially attributed a statement sent by the Senate Conservatives Fund to the Madison Project. It has been updated to reflect the statement the Madison Project released.