Rep. David Schweikert (R-Ariz.) defeated fellow freshman Rep. Ben Quayle (R-Ariz.) in their member-vs-member primary.
Quayle called him to concede, the Arizona Republic reports. The Associated Press has called the race.
According to the most recent results, Schweikert had 53 percent of the vote to Quayle's 47 percent, with nearly 80 percent of precincts reporting.
Schweikert's campaign also sought to make an issue of a recent report that revealed Quayle joined a number of other freshman Republican lawmakers for a late-night swim in the Sea of Galilee, an occurrence that ostensibly broke no rules but drew Quayle off-message for much of the past two weeks.
Schweikert is expected to win in the comfortably Republican district come November.