Silver's latest Senate election map gives McCain a 97.7 percent chance of winning. The most recent poll added to FiveThirtyEight's model comes from Marist College, which found that 55 percent of people in the state said they planned to vote for McCain, 39 percent for Kirkpatrick.)
While it seems likely that McCain will win the race he has described as the "toughest of his life," this is 2016, and anything is possible.
With that in mind, here are the major issues that have defined this campaign:
Like everything in this election season, the U.S. Senate race in Arizona was largely about Donald Trump. Kirkpatrick hit McCain hard for refusing to denounce the GOP nominee after Trump insulted McCain for being a prisoner of war. It seemed to be an effective line of attack, until it wasn't. McCain revoked his support for Trump one day before he and Kirkpatrick engaged in their one televised debate. Coincidence?
The Supreme Court
After the death of Antonin Scalia, McCain joined a chorus of Congressional Republicans in denying President Barack Obama a vote on his choice for a new SCOTUS justice. Most recently, McCain has said that if Hillary Clinton wins, he and others in the GOP will work to block the nomination of any justices she appoints for her entire term, thereby keeping the court in limbo.
This may not have been the first time Planned Parenthood endorsed Kirkpatrick, but when the national nonprofit did so earlier this year, it made sure to tear into John McCain's record on women's issues. Lest we forget, McCain said he'd support a government shutdown if Congress didn't defund Planned Parenthood, and he suffered a brutal Twitter rebuke after refusing to sign a bill allocating money to stop the spread of the zika virus because it didn't defund Planned Parenthood.
The Affordable Care Act
From the beginning, McCain has tied Kirkpatrick to Obamacare, running commercials highlighting an interview in which she said it was her proudest vote. Despite the criticism – and the shrinking number of insurance companies Arizonans have to choose from this year — Kirkpatrick has stood by her vote. Whether this will hurt her in the election remains to be seen.
While McCain tried to resuscitate old campaign attack ads against Kirkpatrick, she used one of his old ads from his last senate race and turned it against him. In both English and Spanish, Kirkpatrick repurposed footage of McCain walking along the southern border with Pinal County Sheriff Paul Babeu. Let's "build the dang fence," McCain says. Alternatively, McCain sought to paint Kirkpatrick as soft on immigration and willing to jeopardize national security by welcoming Syrian refugees. (He also blamed Obama for the crisis.)
Who will better represent Arizona?
If there's one thing people have come to associate with Kirkpatrick, it's her cowboy boots. As New Times noted in a cover story earlier this year, Kirkpatrick makes a point of touting her Arizona roots (and boots) everywhere she goes. Part of the strategy, it seems, is to draw contrast with McCain, who first ran for office in Arizona shortly after moving to the state; Kirkpatrick has dubbed McCain a "Washington insider" and regularly talks about how his time in the nation's capital has changed him for the worse. McCain, meanwhile, has hit back hard, recycling an old attack about how, as a member of the U.S. House of Representatives, "Kirkpatrick turned her back on Arizona voters" — an assertion that fact-checkers have deemed inaccurate — and how she's too liberal for Arizona.