An under-the-radar special election in Alabama next week will provide the first post-shutdown test case for moderate, business-friendly Republicans seeking to neutralize the GOP’s tea party faction that nearly led the country to credit default earlier this month.

The U.S. Chamber of Commerce sent a message to the tea party on Tuesday, when it endorsed an established lawmaker over the tea-party-aligned candidate in the Nov. 5 GOP runoff in Alabama’s 1st District.

So far, the chamber has spent $185,000 to boost former state Sen. Bradley Byrne over Dean Young — effectively laying down a marker in the growing battle for control of the GOP in the midterm cycle.

“It’s the first shot, really the first political shot, in the GOP civil war between the establishment and business community versus the tea party,” Republican consultant Ron Bonjean said.

The chamber has been a major player in congressional elections — it spent about $35 million on federal races last cycle. The group — which boasts that it represents 3 million businesses — endorses around 300 candidates each cycle, according to its national political director, Rob Engstrom.

The chamber mostly supports incumbents, who automatically get the group’s support if they score at least 70 percent on the key votes. But the chamber sometimes plays in open races: For example, it backed businessman John Brunner’s failed primary bid against GOP Rep. Todd Akin in Missouri’s 2012 Senate race.

Engstrom opened the door to more chamber spending in GOP primaries in a Wednesday phone interview with CQ Roll Call.

“For us, what we want is not just to protect the pro-business majority in the House, but a close second to that is what is the composition of that majority and do we have people who come from our family who are constructive and find ways to get things done, especially in this environment?” Engstrom said from Alabama, where he had traveled to back Byrne in person.

The midterm elections provide several options for the group to affect the makeup of the fractured House GOP caucus.

The 2014 cycle features numerous races in strong GOP districts with tea-party-backed candidates going up against more traditional, business-friendly Republicans — such as Minnesota’s 6th District, Georgia’s 10th District and Alabama’s 6th District, plus several Senate races.

In Alabama, the chamber’s endorsement is boosting the otherwise quiet special election to replace former Rep. Jo Bonner. The six-term Republican resigned this summer to take a job with the University of Alabama.

Republicans have long considered Byrne the favorite in a contest that initially had nine GOP candidates vying for the deeply conservative 1st District.

But Young’s second-place finish shook up the race. He won that slot by turning out the district’s social conservative voters with his outspoken opposition to same-sex marriage and close ties with controversial Alabama Supreme Court Chief Justice Roy Moore.

Local operatives said Young would be a departure from the district’s most recent representation in Congress. Both Bonner and his predecessor, Republican Rep. Sonny Callahan, served on the Appropriations Committee.

In a low-turnout runoff, Young has a shot at victory with an engaged evangelical base. During the special election, Young has said he is “against homosexuals pretending like they’re married” and lamented that “we are witnessing the end of a Western Christian empire.”

“Dean Young is one of these sort of unpredictable kind of guys where you don’t know what kind of fight he’s going to get into next week,” said Marty Connors, a local GOP operative and former chairman of the Alabama Republican Party, who said he is neutral in the race. “And that’s not the southern sensibility of the Mobile delta area.”

The 1st District continues to rely heavily on federal funding and contracts. Some local Republicans expressed concern this money could be jeopardized by Young’s hard line against spending. In a recent debate, Young compared himself to Sen. Ted Cruz, R-Texas, the mastermind behind the GOP’s opposition to Obamacare that eventually caused the government shutdown.

“There’s a lot at stake with this member of Congress,” said Alabama GOP consultant Bob Kish, another neutral player in the race. “The district relies a lot on federal money: The harbor needs to be dredged, there are state docks, Airbus is coming in. So there’s billions of dollars flowing in here … and can Dean Young navigate through that?”

The chamber’s endorsement and advertising will help Byrne turn out conservatives from the Mobile area. These suburbs are home to more moderate Republicans and the district’s main television market.

“A few votes can sway the election one way or the other, so I think the ground game is where it’s going to be,” said Alabama GOP Chairman Bill Armistead.

Whoever wins the GOP runoff next week will still have to face Democratic nominee Burton LeFlore in a Dec. 17 general election but will likely become the 1st District’s next representative. Republican presidential nominee Mitt Romney won the district by 24 points in 2012.