Governor Doug Ducey was required by Arizona law to appoint a Republican to fill the vacant seat until a special election winner could be sworn in.

[3] On December 18, 2018, Ducey announced that outgoing U.S. Representative Martha McSally would be appointed to fill the seat following Kyl's resignation.

[5] McSally ran to complete the term, defeating skincare executive Daniel McCarthy in the Republican primary.

As a result, he outperformed Joe Biden in the concurrent presidential election, who defeated President Donald Trump by a margin of 0.3% in the state, but underperformed his polling average.

[8] This also marked the first time since the 82nd Congress preceding the 1952 election that Democrats held both Senate seats in Arizona.