Whoever wins will serve a short term that starts within the next few weeks and runs until the end of the year.
The seat has sat empty for more than five months after Kevin McCarthy stepped down last December just weeks after being ousted as Speaker of the House.
Assemblyman Vince Fong and Tulare County Sheriff Mike Boudreaux, both Republicans, hope to take the seat.
The two are also set to face off in November in a race to secure a full term in office starting next January.
Fong, McCarthy's handpicked successor, is optimistic that his experience working alongside the former House Speaker and in the state assembly will convince people to cast their vote for him.
"When you're electing someone to make national policy on a whole variety of issues," said Fong. "You need someone that has the experience and knowledge and a proven track record to deliver results."
Boudreaux said voters have been telling him they're tired of the status quo.
"There's a lot of people in Kern as well as the Central Valley here, in Tulare, Kings, and Fresno that quite frankly, they're ready for change," said Boudreaux. "They want a different face, they want a new perspective, they want new blood."
Election officials are rooting for a strong voter turnout.
In Fresno County, the estimated cost for both the special election primary and general election is about $550 thousand.
They're hoping for close to 30% voter turnout, by Tuesday morning, they had reached 15%.
"We'll have to see how turnout is today, it's been a little slow at the vote centers this morning, but at our last special election it really kind of picked up as the day went along," said James A. Kus, Fresno County Clerk.
In Kern County, where the majority of voters in the election live, they've spent between $1.1 million and $1.3 million.
In the special election primary, they saw about 26% voter turnout.
As of Tuesday morning, just under 14% of ballots had been returned.
"Potentially, we're experiencing voter fatigue," said Adam Clark, Kern County Spokesperson. "Which you know, this was an unexpected election. So a lot of people weren't prepared for this. So we're hoping that there's a good turnout but so far it's pretty light."
First election results are expected to be posted just after 8 pm.
People can still cast their ballot in person at a vote center or drop it in a drop box until 8 pm Tuesday.
For those voting by mail, it's suggested they walk it into the post office so it's postmarked today.
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