Republican Martha McSally’s path to the U.S. Senate narrowed with Friday’s latest tabulation of votes from Tuesday’s election, which showed Democrat Kyrsten Sinema widening her lead in a race that remains in a tortuous limbo.

McSally's path to victory requires picking up votes in rural counties where she did well, limiting losses in Democratic strongholds such as Pima and Coconino counties, and then winning Maricopa County by a large margin. About 266,000 Maricopa County ballots remain uncounted.

Statewide, about 360,000 ballots remain uncounted.

Sinema's lead over McSally grew to about 20,000 votes as of 7 p.m. Friday.

Sinema is winning the Republican-leaning Maricopa County. When ballots have been tabulated, McSally has not won any batch of votes in Maricopa County, including early votes posted on Election Day, votes cast at polling places on Election Day, and early ballots counted since.

It is unclear if McSally will be able to limit her losses in a meaningful way, even with the legal settlement struck Friday over the handling of certain ballots by county elections officials.

That settlement could favor McSally by helping her pick up votes in counties outside of the more populated areas of the state.

"Equal protection under the law is a fundamental constitutional right for American voters," McSally said in a written statement released Friday night. "As a combat veteran, I fought to protect it. And today, we won an important battle to preserve that right for rural voters in Arizona. I will continue fighting until every ballot is counted."

Sinema, a three-term congresswoman who represents the Phoenix-area’s 9th Congressional District, ran a campaign built around the narrative that she is an “independent” voice for Arizona and distanced herself from other Democrats. That message has likely helped her in Maricopa County, particularly in the suburbs and among moderate women.

McSally, who has represented the Tucson-based 2nd Congressional District for two terms, positioned herself as loyal to President Donald Trump and the Republican agenda, from the health-care overhaul to border security. That message likely solidified her hold on rural Arizona.

“All you can do is wait,” said Larry Sabato, the political scientist who directs the University of Virginia's Center for Politics. “You certainly don’t want to concede until it’s obvious to you and your campaign that you’ve lost. Too many people have put in too much time, resources and money (in the race), so you’ve got to see it through.”

READ MORE: Trump accuses Arizona of election tampering

McSally's fortunes turned after Election Day. She appeared to have the advantage on Tuesday evening, following weeks of barnstorming the state with Republicans of all stripes who vouched for her personal and political credentials.

That advantage continued to melt away on Friday, the second consecutive day of unfavorable early-ballot results from the reporting of tallied votes by the Secretary of State's Office and county recorders.

Andrew Piatt, Sinema's campaign manager, said the data shows Sinema will win the race.

“Once again, today’s data confirmed our expectation that as the ballots are counted, Kyrsten will steadily build her advantage and be elected to the U.S. Senate," he said in a statement. "Nine counties reported today — five of which are counties where McSally is favored and where she needed to perform very well in order to regain even a narrow path to victory. That didn’t happen."

It appears unlikely — but not impossible — that McSally will significantly narrow the gap based on the early ballots that were mailed in before Election Day.

The group of ballots that gave Sinema the lead on Thursday night and kept her there on Friday night favored Democrats. Those early ballots, which were mailed in at the tail-end of the campaign, broke Democratic in a way rarely seen before in this state, said Garrett Archer, a senior data analyst at the Secretary of State's Office.

The Maricopa County Recorder"s Office would not say if early votes were being counted chronologically, as they were received. If they are, Sinema's lead could widen.

McSally’s best bet appears to lie with voters in Maricopa County who dropped their early ballots off at the polls on Election Day.

McSally's campaign explained the theory Thursday night in an email.

“As County Recorders across the state continue to report numbers, the largest tranches left to count are mail-in ballots dropped at the polls on Election Day. We expect these approximately 200,000 votes to strongly favor Martha because significantly more high propensity Republican early voters had not turned in their early ballots as of Election Day."

The email said data modeling showed that as remaining ballots were counted, Sinema's "small lead will disappear."

READ MORE: All Arizona counties to verify ballot signatures through Nov. 14

Archer said people can speculate what the early ballots dropped off at the polls will look like, but no one can know for sure. The early ballots that were mailed in can be estimated because the office has previous returns to base them on, he said.

“No one really knows what the early ballots dropped off at the polls will look like,” Archer said. “It’s impossible to know. … We really have no idea.”

Maricopa County Recorder Adrian Fontes said there are 195,000 early ballots and out of precinct ballots still to be totaled.

Of those, 167,000 ballots were dropped off at the polls, 17,000 were provisional ballots and 11,000 were cast out-of-precinct.

That means McSally would have to make up her margin from a group of early votes in Maricopa that totaled 167,000 votes or less. It’s not impossible for her to do so, especially if she can close the gap before then from more rural counties. For example, McSally won Apache County by nearly 44 percentage points — picking up more than 28,000 votes there.

It’s unclear how many votes are outstanding in Apache County. The Secretary of State’s Office is estimating about 2,000.

READ MORE: Suburban women voters important to McSally, Sinema

But there is another problem McSally will encounter: She needs a decent lead going in to the counting of provisional ballots. Not all provisional votes will count, but those that do are likely to trend Democratic. The effect will be even larger in traditional Democratic counties such as Pima County.

There are 18,000 provisionals in Pima County, 6,800 in Pinal County and 1,000 in Santa Cruz. There are less than 1,000 in a handful of other counties.

Archer said an estimated 85 percent of provisional ballots will count based on experiences from elections in previous years.