One pro-Cruz super PAC said another has boring ads. (AP Photo/LM Otero, File)

A small super PAC supporting the presidential campaign of Sen. Ted Cruz has released a radio ad hitting Sen. Marco Rubio -- in part because they don't like spots another pro-Cruz super PAC is airing.

The Courageous Conservatives PAC created a 60-second radio ad to air in Iowa during talk radio shows slamming Rubio for doing little in the Senate aside from working with others to craft a controversial immigration reform bill that did not pass.

"We all loved how Marco Rubio took apart Jeb Bush in the debate. Wasn’t it great? But what’s Rubio ever done? Anything? Other than his gang of eight amnesty bill, can anyone think of anything Marco Rubio's ever done?" the ad said. "Anything at all besides amnesty? Marco Rubio looks good on TV, but that’s about it."

Rick Shaftan, a consultant for the group, said it was disappointed with radio ads put out this week by Keep the Promise I, a pro-Cruz super PAC funded by hedge fund multimillionaire Robert Mercer that, as of June 30, had $10,470,926 in the bank.

[Read: Cruz super PAC releases radio ads; one boasts about Boehner attack]

"What we want to see is the other pro-Cruz super PACs follow our lead and make ads that reflect the candidate. The candidate is an exciting guy. Boring ads don’t cut it," Shaftan said. "People are concerned that there’s gonna be wimpy ads in defense of Ted Cruz."

The Courageous Conservatives PAC released an ad supporting Ted Cruz to air in Iowa. The 60-second spot slams Marco Rubio for his Senate performance. (YouTube/MountaintopMedia)

"We welcome supporters of Ted Cruz on the air, whether they spend $1 million or $12,000, to inform voters of the Senator's solid conservative principles and winning record. We look forward to working hard to elect Ted Cruz the next President of the United States," Keep the Promise I president Kellyanne Conway said in a statement.

The group released eight radio ads this week as part of a million-dollar buy. The radio ads are running nationally and on local stations in Iowa and South Carolina, two early voting states. The super PAC said they are on faith-based radio networks and will play during conservative talk shows, including "The Rush Limbaugh Show" and Laura Ingraham.

According to the FEC, the Courageous Conservatives PAC has about $5,000 in the bank and is based out of Kansas City. Shaftan said the organization is spending about $12,000 on the ads and Shaftan "just got it wired" to him.

"It’s not anything major but with this little amount of money we’re going to get a big hit in Iowa," he said.