Democratic candidate Kyrsten Sinema increased her advantage over Republican challenger Martha McSally in the Arizona U.S. Senate to more than 32,000 votes Sunday as the state's gradual count continued.

As of 8:30 p.m. ET, Sinema had received 1,071,280 votes statewide, giving her 49.58 percent, according to the Arizona Secretary of State office. Meanwhile, McSally received 1,038,988 votes, giving her 48.07 percent.

In Maricopa County, where approximately 162,000 ballots remained uncounted, Sinema received 649,445 while McSally received 603,070, officials said. Sunday's tally included a batch from Maricopa County, the most populous in the state, that Republicans hoped could help McSally narrow the margin. Instead, it added 2,200 to Sinema's lead.

Late Sunday, Sinema's campaign claimed that the Democrat's lead was "insurmountable."

"Kyrsten has now expanded her overall lead to 32,640 or 1.52 percent, meaning McSally would have to win the remainder of Maricopa ballots by 22 percent to take the lead in this race," Sinema spokesman Andrew Piatt said in a statement. "This is not plausible. Kyrsten will be declared the next U.S. Senator from Arizona."

About 200,000 votes remain uncounted across the state and officials estimate that all ballots won't be tallied until Thursday.

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Ahead of the latest results, McSally’s campaign sent an email to subscribers acknowledging her opponent’s lead in the race and asked supporters for donations to help her “continue to fight and win.”

“The votes are still being tallied, but the latest count shows my liberal opponent has gained a slight edge. There are still more than 300,000 votes left to be counted and I can't slow down now -- Democrats certainly won't,” the email said. "Right now, my opponent's army of attorneys are gearing up for a legal fight to defeat me and I've got to amplify my efforts to cement my victory."

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More than 2.3 million votes were cast in the election.

Fox News’ Alicia Acuna and Melissa Chrise and The Associated Press contributed to this report.