The Chamber of Commerce and National Rifle Association have both endorsed Iowa state Sen. Joni ErnstJoni Kay ErnstMcConnell: Syria strikes were 'appropriate and measured' GOP senator uncomfortable with ground troops in Syria Is Trump an Obama 2.0? MORE (R) in a GOP primary for an open Iowa Senate seat.

The endorsement from the leading business group and the powerful gun lobby give Ernst a boost as she battles businessman Mark Jacobs and two other candidates in the primary.

"Joni understands that big government is an impediment to job creation, and that the best way to turn the economy around and create jobs is through pro-growth economic policies," Chamber Political Director Rob Engstrom said in a statement. "The U.S Chamber is proud to stand with Joni and highlight her work removing regulatory barriers and encouraging competition in Iowa. In today’s economy, that’s the type of leadership we need in Washington."

Ernst has rallied both establishment and Tea Party Republicans to her cause as she seeks to beat Jacobs, a self-funding candidate who has dominated the airwaves.

Ernst has been able to earn a lot of free media with her edgy ads, including one that said she grew on an Iowa farm "castrating hogs" and another where she rides a Harley Davidson to a gun range and "takes aim" at ObamaCare.

"Joni  Ernst has consistently opposed all attempts to restrict gun rights and has been a true friend of the Second Amendment," said NRA Political Victory Fund Chairman Chris Cox. "She is one great example of NRA moms all across this country fighting for our freedoms. She's the only candidate in this race with a proven record of defending our rights.  I urge all NRA members, gun-owners, and sportsmen in Iowa to vote for Joni Ernst in the June 3rd Republican primary."

She also has endorsements from former Alaska Gov. Sarah Palin (R), 2012 presidential nominee Mitt Romney (R) and the Senate Conservatives Fund, among other groups.

But she's still short on money, and the Chamber has spent heavily to back its preferred candidates in other primaries. If they put ads in Iowa behind Ernst, it could help boost her ahead of the June 3 primary.

The winner of the primary will face Rep. Bruce Braley (D-Iowa) in the swing state.

— This post was updated at 11:45 a.m.