The Arizona Republic is backing Rep. Kyrsten Sinema (D-Ariz.) in her contentious Senate race against Rep. Martha McSally Martha Elizabeth McSallyThe Hill's Campaign Report: Presidential polls tighten weeks out from Election Day Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' New ABC/WaPost poll finds Trump edging Biden in Arizona, Florida MORE (R-Ariz.), the paper announced in an editorial on Sunday.

The endorsement of Sinema is the paper's first for a Democrat in a statewide Senate race since at least 2000, according to Axios. The Arizona Republic first backed a Democrat for any office in the 2016 when it endorsed Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE in her presidential bid.

Rather than pointing to particular policy positions in the endorsement, the editorial board pointed to how the candidates have handled themselves during the race.

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"We need to get back to a saner time, when senators didn’t call each other names — or if they did, they could put it all aside after the vote and go get a beer together," the paper's editorial board wrote. "There is too much 'us and them' in D.C., and it hurts how we are governed."

"The real Martha McSally and Kyrsten Sinema know that," the board argued. "But Sinema is the only one willing to say it (repeatedly) from behind her mask."

The editorial board argued that McSally has gone further than Sinema in attacks on her opponent.

"There may be no better example of politics by collaboration than Sinema," the paper's editorial board wrote, also pointing out that over 60 percent of the bills she has co-sponsored this session were introduced by Republicans and that Sinema sides "with Trump's agenda 62 percent of the time."

"She has traveled a long ways from the street-marching activist she once was to the good-natured centrist she now is," the paper's board said. "In a Washington in which rancor and malice are disturbingly normal, Sinema is the antidote."

The unprecedented endorsement comes with the election only weeks away and Sinema and McSally caught in a statistical tie in polling.