Lupe Castillo is running against Patty Garcia (D, likely nominee - chief of staff to outgoing Rep. Chuy Garcia); Byron Sigcho-Lopez (I, progressive alderman); Mayra Macias (I, endorsed by Rep. Nydia Velazquez).
IL-04 is a D+17 district, heavily Democratic and 55% Hispanic. Incumbent Chuy Garcia announced his retirement in November 2025, timing it to ensure his chief of staff Patty Garcia was the only Democrat on the primary ballot. The Chicago Tribune criticized this as "machine-style" politics. Castillo is the lone Republican running for a seat that would require a major upset to flip.
Castillo lost to Garcia in 2024 with 27.3% of the vote. Two independents are running: progressive alderman Byron Sigcho-Lopez and former Latino Victory Fund executive Mayra Macias, both frozen out of the Democratic primary by Garcia's timing.
Key dates to watch: Primary on March 17, 2026 and General Election on November 3, 2026.