An ex-congressman, a state lawmaker, an online news personality and a former combat pilot are among the candidates hoping to fill a U.S. House seat north of Los Angeles — a race that’s being watched nationally for hints about which party might control Congress next year.

The swing 25th District that cuts through swaths of suburbs and small horse ranches was left vacant last year after first-term Democrat Katie Hill resigned amid a House ethics probe and sex scandal.

Republicans want the seat back, while Democrats believe they have a strong chance to hold it, despite its history as Republican-leaning terrain. In a twist that could confuse voters Tuesday, the ballot will include two elections for the seat. One is a special election to choose someone to complete the second year of Hill’s term. The other is a race to choose two candidates to advance to the November general election that will determine who takes the seat in 2021.

On the Republican side, the candidates in both races include former U.S. Rep. Steve Knight, who lost the seat to Hill two years ago; former Navy pilot Mike Garcia; and former Trump campaign aide George Papadopoulos, who served a two-week prison sentence for lying to the FBI about his interactions with Russian intermediaries during the 2016 campaign. The Democratic field includes Christy Smith, a state assemblywoman backed by the party establishment, and online news personality and progressive Cenk Uygur.

If no candidate wins more than 50% of the special election vote — the threshold to claim the seat — then the top-two vote-getters would be matched up in another special election in May.

The Democratic contest looks similar to the 2020 presidential race, with a split between the party’s center-left and progressive ranks. Knight and Garcia, meanwhile, have dueled over loyalty to President Donald Trump.

The district was long considered GOP terrain before Hill’s victory, and like much of California, it has been growing gradually more Democratic in voter registration. Democrats hold a 6-point registration edge in the district, which runs through northern Los Angeles County but also takes in a GOP-rich pocket in Ventura County, including the Ronald Reagan Presidential Library.

In a telling sign of change, Hillary Clinton carried the district by nearly 7 points in the 2016 presidential election. Two years later, Hill claimed what was then the last Republican-held House seat anchored in Los Angeles County with a 9-point win.

The district is among a string of California House seats that Republicans hope they can reclaim in 2020, including four all or partly in the former GOP stronghold of Orange County.

Of the state’s 53 congressional seats, only six are held by the GOP.