Nevada’s high-profile Senate and gubernatorial races remain up in the air, with tens of thousands of ballots to be counted over the next week in key counties that could eat away at GOP leads.

The exact number of ballots still to be reported remains unclear. Officials sent mail-in ballots to “active” registered voters unless they opted out, and mail ballots that arrive before Saturday at 5 p.m. local time will be counted, as long as they were postmarked by Election Day

Additionally, voters whose mail ballot signatures did not match state records have until Monday evening to “cure” their signature so their votes can be counted. Provisional ballots won’t be counted until next week. Election officials are still processing tens of thousands of ballots they already received, with many expected to be Democratic-leaning.

If those expectations hold accurate, Republican Senate nominee Adam Laxalt’s roughly 16,000-vote lead and Republican gubernatorial nominee Joe Lombardo’s roughly 34,000-vote lead could shrink or perhaps give Democrats victories.

Whatever the outcome, Nevada’s Senate race holds key implications for control of the upper chamber. 

If Democrats or Republicans win both of the two remaining races up for grabs — Arizona and Nevada — they win a majority. If the two races split, Georgia’s runoff election next month will become the pinnacle contest.

Counting in Arizona is also expected to stretch into next week.

As votes keep trickling in, here are two key Nevada counties to watch:

Clark County

Clark County, which includes Las Vegas and the southernmost part of the state, comprises nearly 73 percent of Nevada’s population, the highest proportion of a state’s population of any county in the country.

Due to its reliably blue electorate, The Nevada Independent’s Jon Ralston has called the county the “Clark Dem firewall.”

Democratic presidential candidate Hillary Clinton won the county by nearly 11 points in 2016, and President Biden by 9 points in 2020.

But as of Thursday afternoon, Sen. Catherine Cortez Masto (D) only leads Laxalt by 5 points in the county, and Gov. Steve Sisolak (D) leads Lombardo there by 3 points.

Joe Gloria, Clark County’s registrar of voters, said at a Thursday press conference that just more than 50,000 ballots remain uncounted, all of which are mail ballots, and he expects most will be reported by Saturday.

Democrats are hoping those mail votes will improve their margins and outweigh the GOP’s current lead, along with remaining gains in red, rural counties.

Clark County is reporting new votes nightly, and Wednesday evening’s batch of 14,092 ballots broke for Democrats by a roughly 2-to-1 margin.

But Gloria said counting will stretch into next week, because ballots can still arrive in the mail through Saturday — 626 were received on Thursday alone — and 7,155 Clark voters have until Monday to “cure” their mismatched mail ballot signature. Another 5,555 provisional ballots have yet to be rectified for other reasons.

“There are statutory deadlines here that prevent me from finishing any earlier than the general public or you, the media, would like to see us work,” Gloria said. “I can’t stop until Saturday for the mail. I can’t stop until Monday for the cure. I can’t count provisionals until next Wednesday at the earliest.”

Despite Democrats’ recent gains in the latest Clark County vote batch, Laxalt was skeptical she could take the lead.

“Of the 84,000 votes left to count in Clark County, Cortez Masto could win 63% of them and she would still lose,” Laxalt tweeted Thursday morning. “That doesn’t even take into account the gains we will make from rural counties.”

“Last night went exactly as we anticipated,” Laxalt continued. “We added 3K from the rurals and more are coming. She added some Clark County mail. We expect the remaining mail universe to fall well below the percentage she needs to catch us. No status change.”

Washoe County

Washoe County, which encompasses Reno and stretches north to the Oregon-Nevada border, is the state’s only other county that former President Trump lost in both 2016 and 2020.

Biden won the county by 5 percentage points, and Hillary Clinton won there by just 1 point, making Washoe a key battleground in the swing state.

Washoe also is Nevada’s second-most populous county, comprising nearly 16 percent of the population, according to U.S. Census Bureau estimates. Combined with Clark, nearly 9 in 10 state residents live in the two counties.

Washoe’s reported results so far show a nearly even split. Cortez Masto leads Laxalt by 0.2 percent in Washoe, while Lombardo leads Sisolak by 2 percent.

Like Clark, Washoe also has yet to report tens of thousands of mail ballots.

The county’s data shows it has received 102,470 mail ballots so far, but Washoe has only reported the results of 60,828 of those votes.

Washoe election officials said in a Thursday statement that a “small update” will be posted in the evening, but the “bulk” of the ballots will be reported on Friday.

“My focus is to count ballots accurately, not quickly,” Washoe County interim Registrar Jamie Rodriguez said.

Washoe officials indicated Thursday’s delivery of new mail ballots exceeded expectations, reaching roughly 4,500 new ballots. 

Roughly 1,400 ballots in the county are awaiting a signature cure, an additional few hundred “suspended” ballots will be processed after others are tabulated and a further few hundred are damaged and will be duplicated by a bipartisan board for counting, officials said.