Mr. Kelly, who won office in 2020 in a special election to fill the seat of Senator John McCain after his death, will be serving his first full term. In the final weeks of the campaign, his allies promoted Mr. Kelly’s bipartisan work in the Senate on energy, infrastructure and the economy. Outside the Arizona State Capitol a day before Election Day, Mr. McCain’s sons stood with state Republican leaders and former elected officials, who accused Mr. Masters of campaigning on fear and rebuked him over his 2020 election claims.
Sharon Harper, who is close friends with the McCain family and serves as the chief executive of a Peoria commercial real estate company, said at the event that she knew Mr. McCain would have been “very supportive” of Mr. Kelly because, like Mr. McCain, Mr. Kelly always put “America and Arizona first.”
Mr. Kelly, a former astronaut and the founder of a nonprofit group and super PAC that support gun control — his wife, former Representative Gabby Giffords, was shot in the head in a 2011 assassination attempt — pitched himself as a leader concerned first and foremost with the needs of his state. He received help from former President Barack Obama and Jill Biden, the first lady, who made last-minute stops in Arizona.
But given President Biden’s sagging approval ratings and what appeared to be a difficult national environment for Democrats, Mr. Kelly was vulnerable.
In an October debate, Mr. Masters hit him hard on inflation and the southern border, two of Republicans’ strongest issues in the state. On the stump, Mr. Masters painted a dystopian picture of the border — overrun by cartels, fentanyl and “illegals” sweeping through.
After lagging well behind in polls early in the campaign, Mr. Masters improved his standing as former President Donald J. Trump and his allies came to his aid and national Republicans ticked up their ad spending.
Some Republican political strategists also saw Mr. Masters as riding the coattails of Kari Lake, the Republican running for Arizona governor, whose race against Katie Hobbs, the Democratic secretary of state, remained too close to call on Friday.