For Kyrsten Sinema and Martha McSally, Tuesday night was supposed to mark the end of a hard-fought battle that tested vastly different visions for the nation.

But as Election Day came to an end, the race for Arizona's open U.S. Senate seat ended exactly how it has played out over the past few weeks: too close to call.

An official victor may not be known for days — and maybe longer, if the final tally were to trigger a recount or legal challenge, experts say. As Tuesday night ticked toward Wednesday morning, the lack of an outcome began to settle in. 

Maricopa County Recorder's Office officials were expected to receive data from polling locations well into the night, said spokeswoman Murphy Hebert. The system will be updated as the ballots are processed, she said. Those data reflect in-person votes cast on Election Day.

The office will then start processing the "late early ballots," which include those dropped off at the polling places on election day.

"That's going to take days," Hebert said.

MORE: McSally, Sinema locked in too-close-to-call race for U.S. Senate seat

She said the recorder will not update results on Wednesday because of the lengthy signature-verification process. The next scheduled update is at 5 p.m. on Thursday and then every day at 5 p.m. until the office is done counting ballots.

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If the results remain superclose between the congresswomen, attorneys for the Democratic and Republican parties almost certainly will swarm the offices of county recorders on Wednesday morning, seeking to watch their processes, said Eric Spencer, the state elections director.

He is familiar with the post-Election Day playbook from his days in private practice, when he represented candidates and political parties. No matter how well or how poorly an election is conducted, he said, either side may make claims to take their case to court.

"There are going to be very sophisticated operations of monitoring and reporting that stuff back to the parties," he said. "And it's inevitable there will be some sort of lawsuit filed during the process."