(Photo via mccain.senate.gov)

Sen. John McCain.

Republicans who control the Arizona Senate were prevented from ensuring that ailing Sen. John McCain's seat isn't on the November ballot if he leaves office.

Minority Democrats voted as a block on Monday against House Bill 2538, preventing an emergency clause from being tacked onto legislation changing how members of Congress who die or resign are replaced.

McCain has brain cancer and has been recovering in Arizona since December. He was hospitalized for an intestinal infection on April 15. His wife posted on Twitter that the senator was home Monday at his family ranch near Sedona.

Senate vacancies are filled by a governor's appointee, with the seat on the next general election ballot. Current law says his seat would be on this year's ballot if he leaves office by May 30.