The race has been closely watched, with a miniscule margin between the two candidates who are vying for the seat of retiring Republican Sen. Jeff Flake.
On Saturday evening, Sinema stood more than 28,000 votes ahead of McSally, with 49.5% of the vote for Sinema and 48.2% for McSally.
The most recent tally has 88% of votes reported, but individual counties in Arizona are expected to continue to update their vote counts periodically until the votes are certified.
Sinema pulled slightly ahead of McSally this week after roughly 127,000 votes in Maricopa County — the state’s most populous county and home to Phoenix — were counted Thursday.
Whoever wins will be the first woman to represent Arizona in the Senate.