Two County Tallies in Nevada Show Democratic Route to Senate

The Democratic Party’s path to holding the U.S. Senate — even without winning the runoff election that is coming in Georgia — became clearer on Wednesday night as the first post-election vote tallies in Nevada and Arizona showed Democrats faring well among mail voters.

In Nevada, Senator Catherine Cortez Masto, a Democrat, carried the first round of mail ballots in Clark County, which includes Las Vegas, and Washoe County, home to Reno, by two to one.

The total number of remaining ballots in Nevada is murky, because the state does not release authoritative data. Clark County alone had 50,000 still to tabulate as of Thursday, with another estimated 40,000 across Nevada, which can continue to receive mail-in ballots until Saturday as long as they were postmarked by Tuesday. If the estimate is correct — and if Ms. Cortez Masto continues to pick up these ballots by such a wide margin — it would be more than enough for the senator to overcome her deficit in the current tabulated count.

If the Democrats take Nevada and also hang on to Arizona, where the Democratic candidate, Senator Mark Kelly, holds a wider, five-point lead so far, the Democrats would keep control of the U.S. Senate. Wins in Nevada and Arizona would mean that Democrats would not need to wait for the result of a runoff in Georgia to maintain control of the chamber.

Mr. Kelly’s chances of maintaining his lead appeared to improve last night, because Democrats fared well in the first tallies of mail ballots that voters returned before Election Day. Overall, Mr. Kelly won last night’s tally in Maricopa County, the state’s largest and home to Phoenix, by a 15-point margin — an even greater lead than his margin in all the votes counted so far in Arizona.

The ballots at once expanded Mr. Kelly’s lead in the race for U.S. Senate and raised the burden on the Republican, Blake Masters, to come out ahead in the approximately 600,000 votes that remain to be counted.

Mr. Masters can hope to perform better among the mail ballots that were returned on Election Day, which remain to be counted. President Donald J. Trump excelled among similar batches of voters in 2020, when he nearly overcame Joseph R. Biden Jr.’s early lead on election night. But Mr. Trump also won the first batches of late votes, like those tabulated Wednesday night.

To be elected, Mr. Masters needs to win the remaining vote by at least a 15-point margin. Without additional data on the remaining ballots, news organizations will probably not make a projection for Mr. Kelly until the burden on Mr. Masters is far greater. Still, his path to victory will look long until he demonstrates major strength in the late count.