"We're on the move. The 'blue wave' is a reality," Fran Sdao, chair of the Democratic Party of Orange County said as volunteers made calls from the party headquarters in Orange.
"The Republican wave, the 'red wave,' is the one you'll see in June," Fred Whitaker, the chair of the Republican Party of Orange County, countered as dozens of Republican Party volunteers worked the phone banks in Yorba Linda, with less than 24 hours before the primary election.
Democrats are hopeful after the 2016 election, when for first time in 80 years the majority of Orange County voted for a Democrat, Hillary Clinton.
Orange County voting information: https://www.ocvote.com
In the 39th Congressional District, which includes north O.C. and parts of Los Angeles and San Bernardino counties, Republican Rep. Ed Royce is not seeking re-election after 25 years. Neither is Republican Darrell Issa, who served in Congress since 2001 representing the 49th District which includes south Orange County and part of San Diego County.
"You can't overstate the significance of those races either, because either one of those races could end up determining who controls the House," said David Siders, a senior reporter with Politico.
In the 45th District, incumbent Mimi Walters, the only Republican on the ballot, faces four Democrats and one Independent.
One of the most competitive races is the 48th District, which includes most of Orange County's coast. Republican Dana Rohrabacher has held the seat for 30 years, criticized by opponents for his pro-Russia stance.
In the past, he said his interest in closer ties with Russia is a legitimate part of his work as chair of the House Foreign Affairs Subcommittee that has jurisdiction over Russia and other parts of the world.
"All of our polling shows him way ahead," said Whitaker.
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Whitaker said the issue of Russia has little effect on the race as voters are more concerned about things like repealing the gas tax.
"We're able to cross over and get lots of voters who may not have voted with us in 2016," said Whitaker.
Voters face a crowded field of candidates. Seventeen are on the ballot for the 48th District. Though some have dropped out, their names are still listed. Seventeen candidates are also running to replace Royce, and 16 are vying for Issa's seat.
"They have some problems in the primary with these multiple Democrats, big Democratic field, perhaps winnowing the vote," said Siders.
California's unique top two primary system could hurt Democrats if the top two vote getters in the primary end up being Republicans. They would advance to the general election, shutting out the Democrats.
"Very concerned," said Sdao. "We know in the 45th, we're going to get a Democrat because there's only one Republican. In the other three (races), it's very worrisome."
Races are dominated on the Democratic side by first-timers with money.
According to Federal Election Commission figures, Democrats in the 39th, 48th and 49th districts have raised more than $20 million - more than $16 million are from the candidates' own pockets.
In the same three races, more than $10 million of outside money came from Democratic groups -- that's nearly five times more than from Republicans.
Both sides say the key is getting people to vote. Traditionally, primaries see low turnout.
"Historically primary elections are better for Republicans than Democrats," said Siders.
"Generally it does, but these are not normal times. We're in unchartered territory here," said Sdao