Angela Green, a Green Party candidate, was running a distant third, with just over 2 percent of the vote.
Sinema and her allies in the Democratic Party repeatedly called out McSally for swerving to the right and embracing President Trump - even after McSally handily defeated her hardline rivals Kelli Ward and Joe Arpaio in the August primary.
The race between Republican Martha McSally and Democrat Kyrsten Sinema for U.S. Senate was too close to call Tuesday night.
An official victor may not be known for days - and maybe longer if the final tally triggers a recount or legal challenge, experts said. Both candidates said nothing publicly Tuesday night as the ballots were slowly counted. He also expected Republicans to maintain a narrow hold on the Senate. There was no sign of Sinema, as winning Congressional District 9 candidate Greg Stanton and losing gubernatorial candidate David Garcia crossed the stage to give their speeches. McSally lost her first general election by less than 200 votes and won her second by about that many, and Sinema also represents a competitive swing district.
The avid triathletes are battling over the seat vacated by Sen. Both Sinema and McSally had served in the U.S. House and are vying for the seat now held by Republican Jeff Flake, who is retiring.
Oregon's Midterm Voter Turnout Approaching Presidential Election Level
Voters needing to vote absentee in person must go to the office for the locality in which they are registered to vote. State elections officials say Saturday afternoon's vote count will be updated as more counties report totals.
Kyrsten Sinema and Martha McSally.
Many Democrats have been critical of Trump's decision to send troops to the border, but a poll from Rasmussen shows that 50 percent of Americans support the decision. She has tried to rally Republican voters by emphasizing her military background as the first USA female combat pilot while touting her support for the president's tax cut and other parts of his agenda. The repeal of the Affordable Care Act, which didn't become law, would have weakened protections for people with pre-existing conditions. Republican ads publicized a 2010 video of Sinema repeating a comedian's description of Arizona as "the meth lab of democracy". She remained optimistic about a Sinema victory.
Flake won his U.S. Senate election in 2012 by 3.5 percentage points.
If she wins, her campaign could become a centrist blueprint for Democrats eager to win in deep-red Republican strongholds.
The Senate race will test that theory and may help determine whether Democrats target Arizona in the 2020 presidential election.