Now it falls to Ducey to choose McCain's successor. The first-term governor has already begun considering a list of potential replacements, according to four Republicans either familiar with Ducey's thinking or close to those who have been involved in initial discussions.

ADVERTISEMENT But Ducey, both conscious of McCain's status as one of the nation's most respected statesmen and war heroes and nervous about his own reelection bid this November, has squelched speculation about who might inherit McCain's seat.

A spokesman in Ducey's office declined to comment. None of the Republicans familiar with Ducey's thinking agreed to speak on the record, in order to detail private and sensitive conversations.

Most speculation focused on three potential candidates: Maj. Gen. Michael McGuire, the director of the Arizona Department of Emergency and Military Affairs and the adjutant general of the state's Army and Air National Guards; Karrin Taylor Robson, a wealthy businesswoman whom Ducey appointed to the state Board of Regents in 2017; and Kirk Adams, a former state House Speaker who is now Ducey's chief of staff.

Several sources also pointed to former Sen. Jon Kyl (R), McCain's longtime seatmate who is now shepherding Judge Brett Kavanaugh's nomination to the Supreme Court, and former Rep. John Shadegg (R), who left Congress in 2011.

The New York Times on Sunday added state Treasurer Eileen Klein (R) and Barbara Barrett, an ambassador to Finland under former President George W. Bush.

Those relationships mean that other potential Senate candidates once thought to be under consideration have fallen victim to political circumstance.

Several potential candidates who began jockeying for an appointment late last year were so public about their ostensibly private bids that they effectively played themselves out of contention. In a radio interview last year, Ducey said those who were "openly lobbying for this position, they've basically disqualified themselves by showing their true character."

Whomever Ducey chooses to replace McCain will serve in the Senate until 2020, when Arizona voters will choose someone to fill the two remaining years of the term McCain won in 2016.