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.

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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.

If the results remain super close 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."

Word of a prolonged decision disappointed voters like Rosa Sandoval, who stood at a tabletop in the ballroom of the Democratic election night party, looking glum.

She drove into downtown Phoenix from Queen Creek hoping to celebrate a Democratic Senate win.

"It's nerve-racking," said Sandoval, who works at an equine hospital. "I'm optimistic. I really think Sinema is going to win."

Court battle

One side or the other could test claims of voter disenfranchisement in court if the race comes down to a narrow margin, Spencer said.

Already the state Republican Party has warned of potential legal action over about 3,000 ballots cast in Maricopa County "emergency vote centers."

And the Lawyers' Committee for Civil Rights Under Law, the Arizona Advocacy Foundation and All Voting is Local-Arizona lost a last-minute demand in court on Tuesday evening to try to force Maricopa County to extend voting hours, given the day's glitches.

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Maricopa County's top election official, Recorder Adrian Fontes, a Democrat, oversaw his first general-election following a bumpy primary cycle. During the Aug. 28 primary election, many people could not vote because voter check-in equipment was improperly installed at more than five dozen polling places.

Fontes' last performance sets up the potential for wariness among Republican party officials in the state's most populous county. Other counties have had histories of late returns or ballot issues of their own.

Either side could allege voting processes violate equal-protection violations of the U.S. Constitution.

"The political parties will chase after every vote that remains in limbo and someone is going to file a lawsuit claiming that whatever process is being used is disenfranchising their voter," Spencer said.

He expects either party to request public information from county recorders under the Arizona Public Records Law to seek to determine reporting discrepancies between official vote tallies and voters who cast ballots provisionally and those who voted early.

"The parties will spend the next five to seven days trying to chase those people down, and alter the results in some small way ... The reality is that someone will go to federal court and argue that x group of ballots and y group of ballots should or should not be counted."

Recount?

Recounts in statewide races don't happen very often.

An automatic recount is required when the results from the official canvass show that the difference in total votes cast for McSally and Sinema is less than or equal to the lesser amount of one-tenth of 1 percent, or 200 votes.

The secretary of state is scheduled to canvass the results Dec. 3.

If the race falls within the margins, said Spencer, "we will literally leave the canvass on the morning of Dec. 3 and literally go to the courthouse and file a lawsuit" to formalize the legal recount process.

A recount of the ballots would begin almost immediately, following a judicial order.

In 2010, a statewide ballot measure known as Proposition 112 that sought to shorten the filing deadline for initiative petitions, triggered a mandatory recount. It wound up being rejected by 194 votes, a margin greater than the 128 votes that it appeared to lose by in the initial count.

And in the 1994 Democratic primary for U.S. Senate, then-U.S. Rep. Sam Coppersmith edged then-Arizona Secretary of State Dick Mahoney by 132 votes.

That recount confirmed a 59-vote victory for Coppersmith, who went on to lose the general election against then-U.S. Rep. Jon Kyl, R-Ariz.

Kyl would go on to serve three Senate terms before returning to the chamber again in September following an appointment by Gov. Doug Ducey after the death of U.S. Sen. John McCain.

Follow the reporter on Twitter and Facebook. Contact her at yvonne.wingett@arizonarepublic.com.