A couple of dozen observers from the campaigns of Congressman Ami Bera and Doug Ose as well as national political parties are challenging thousands of mail-in ballots.
The Sacramento County voting offices routinely allows people to watch them count ballots.
But the hotly contested race which broke campaign spending records has required voting office staffers to create a specialized team to rule on ballot challenges. That usually entails matching signatures on the ballots with signatures on voter registration documents or other sources.
Kim Alexander, President of the California Voter Foundation, was observing the observers. She says campaigns try to use every advantage they can to win tight races, including utilizing challenges.
"There can be a lot of strategy involved there based on particular precincts, based on voters with different surnames so its an issue keep an eye on because we don't want to see anyone disenfranchised," said Alexander.
She worries about how vote counters will react to the pressure.
"Sacramento may also be rejecting more ballots because they've got these election observers who are standing over their shoulders telling them that 'we disagree'," said Alexander.
When the polls closed on Tuesday, Ose lead Bera by around 3,000 votes. But in the last election, Bera picked up around 9,000 votes once mail-in ballots were counted. Ose's camp believe this year the mail-ins are trending 50/50, which would give Ose the victory.
A recount can be requested once the election is certified, but the party requesting a recount would have to pay for it.