Orange County a key battleground for congressional races

SANTA ANA, Calif. (KABC) -- Several congressional races in Orange County are getting national attention as Democrats seek to gain ground in the historically Republican stronghold.

The Orange County Registrar of Voters office says while in-person voting numbers have been relatively low so far Tuesday, the vote-by-mail numbers are higher than what was seen in 2014.

Orange County voting information: https://www.ocvote.com

The agency expects to have about 240 employees keeping busy long through the night counting votes and monitoring polling issues.

"In the congressional districts in particular we're putting extra resources and attention on that because we expected higher turnout," said Registrar of Voters Neal Kelley. "We're ready for that. So at the end of the night we have more folks to bring that stuff in earlier."

MORE: California primary voting polls open in SoCal - What to know

Polls are open across California on Tuesday, as voters decide on who will be the final two candidates in the governor and senate races.

Among the key congressional races in Orange County are the 39th district, where longtime Republican Rep. Ed Royce is not seeking re-election after 25 years; the 49th District, where Republican Darrell Issa is also leaving Congress; the 45th District, where incumbent Rep. Mimi Walters is facing challenges from four Democrats and an independent; and the 48th District, where incumbent Rep. Dana Rohrabacher has held the seat for 30 years.