The Club for Growth said Tuesday it won't help Rep. Steve StockmanStephen (Steve) Ernest StockmanSpaceX launch is step one in a new American-dominated space race McConnell must go nuclear: Abolish the legislative filibuster Ex-GOP staffer pleads guilty to fraud, money laundering on behalf of ex-lawmaker MORE's (R-Texas) primary challenge against Sen. John CornynJohn CornynLawmakers feel pressure on guns Kasich’s campaign website tones down gun language after Florida shooting Murphy: Trump’s support for background check bill shows gun politics ‘shifting rapidly’ MORE (R-Texas).

The conservative group said it has no problem with Cornyn and won't spend the millions of dollars necessary to help the cash-strapped Stockman in the race.

“While Congressman Stockman has a pro-economic growth record, so does Senator Cornyn, as witnessed by his 87 percent lifetime Club for Growth score,” President Chris Chocola said in a statement.

Chocola said the Club's political action committee looks at the strength of the incumbent's record, the degree of difference between the candidates and the viability of a challenger in deciding whether to get involved in a race against an incumbent.

"None of those factors weigh against Senator Cornyn, so we do not expect to be involved in the Texas Senate race,” he said.

The Club spent millions of dollars to help Sen. Ted Cruz (R-Texas) pull off an upset primary win over Texas Lt. Gov. David Dewhurst (R) last year, and is the best-funded of the conservative groups that play in GOP primaries. 

Stockman, in a surprise move, announced Monday that he would challenge Cornyn rather than seek reelection.

The outspoken conservative entered the race shortly before Texas's filing deadline, and with just $32,000 in cash on hand and $163,000 in debt.

Cornyn has nearly $7 million cash on hand for the race.

Texas is one of the most expensive states in the country to campaign in, and can cost as much as $1.5 million a week for major television advertising.

The Club's decision to stay out of the race undercuts Stockman's argument that the incumbent isn't conservative enough. Stockman attacked Cornyn for breaking with Cruz in his fight to defund ObamaCare by forcing a government shutdown earlier this year.

"We are extremely disappointed in the way he treated his fellow congressmen and broke the 11th commandment and undermined Ted Cruz’s fight to stop ObamCcare," Stockman said Monday, citing former President Reagan's well-known guideline that Republicans shouldn't speak ill of other Republicans.

The primary is in early March, meaning Stockman will have to rev up his fundraising in a huge way to be competitive in the race.

While the Club has ruled out helping him, other conservative groups could still get involved. The Senate Conservatives Fund said it's taking a look at the race on Monday.