Arizona is a reliable Republican state in presidential elections, but Democrats are contesting it. There is a statewide race for U.S. Senate this year. Republican incumbent Martha McSally, appointed to fill the vacancy left by the late Sen. John McCain, is running for a full term. The state has nine congressional districts. Arizona voters unaffiliated with a party can participate in either major party primary for state and congressional offices. Presidential primaries are closed, meaning that only registered Republicans or Democrats may vote in the major party primaries.