The Republican-controlled Arizona Legislature is moving to ensure that ailing Sen. John McCain's seat isn't on the November ballot if he leaves office, but Democrats plan to block the effort.

The effort emerged Tuesday as the state Senate put an emergency clause on a bill changing how members of Congress who die or resign are replaced.

U.S. Senate vacancies are filled by a governor's appointee, with the seat on the next general election ballot. The secretary of state has interpreted that to mean that if McCain's seat is vacated by May 31, it would be on the August primary and November general election ballot. The new proposal changes that to 150 days before the primary, or March 31 of this year. That takes McCain's seat out of play.

McCain was diagnosed with brain cancer last summer and has been recovering in Arizona since before Christmas. He was hospitalized over the weekend for intestinal surgery needed to stem an infection and remains in a Phoenix hospital in stable condition.

The emergency clause requires a two-thirds vote, and Democratic Sen. Steve Farley said that won't happen.

"They're trying to make it really easy to appoint someone to two and a half years without an election to a U.S. Senate seat should the current holder of that Senate seat resign or no longer be able to hold office," Farley said. "The thing is, we're all going to vote against it as Democrats, so they won't get their emergency. It's silly for them to put it on and think we won't notice."

Republicans already are defending one Arizona U.S. Senate seat in November after Jeff Flake decided not to see re-election. Three prominent Republicans are seeking the GOP nomination, and Democratic Rep. Kyrsten Sinema is the front-runner for her party's nomination.

Having a second Senate seat to defend would double the chances that Democrats could pick up an Arizona Senate seat for the first time since Dennis DiConcini left office in 1995.

It's unclear exactly who is pushing for the change, although Farley speculated it was Republican Gov. Doug Ducey. Ducey spokesman Daniel Scarpinato didn't immediately return calls seeking comment Tuesday afternoon.

Republican Sen. Sonny Borrelli carried Tuesday's floor amendment, saying it was important to "be prepared." But he discounted questions about protecting McCain's seat.

"That's assuming that something is going to happen to John McCain," Borrelli said. "This is a man who survived Hanoi, spent his entire adult life serving his country, has got a very strong constitution. If there's one guy on this planet who can beat this cancer, it will be him."

The Legislation was originally intended to lengthen the time required for a special election for a vacant U.S. House seat and was prompted by the scramble to replace Trent Franks, a longtime Congressman who stepped down in December amid sexual misconduct allegations. House members who leave office trigger a snap special election with no appointment by the governor. Democrats in the House added the change in Senate replacement rules, not anticipating the emergency clause, Rep. Ken Clark said.

The measure advanced Tuesday still requires a formal Senate vote before returning to the House.