Representative Barry Moore, an early backer of the president during his first campaign, faces Jared Hudson, a former Navy SEAL tapping into the excitement for outsiders.
Gathering in Tehran earlier this month., Iran affirmed in the agreement that it would never seek to build or procure a nuclear weapon, but the regime has made that promise many times previously.
Mr. Trump backed Mr. Collins over Derek Dooley, a former football coach supported by Gov. Brian Kemp, a Republican whose relationship with the president is strained.