The competitive dynamics of Iowa’s 3rd Congressional District, a suburban swing seat anchored in the Des Moines metro, underpin current trader positioning favoring the Democratic nominee at 68.5% implied probability over the Republican incumbent at 45%. Zach Nunn secured the GOP nomination without opposition in the June 2 primary after his narrow 2024 reelection, while Sarah Trone Garriott consolidated Democratic support by winning her primary by a wide margin following earlier candidate withdrawals and endorsements. Recent head-to-head polling has shown the race within single digits or with a modest Democratic edge, consistent with the district’s history of close results and its status as a targeted battleground in the 2026 midterms. No major late-breaking developments have altered the balance since the primaries, leaving voter turnout, campaign spending, and national conditions as the primary variables that could shift the outcome before November.