The Pennsylvania Senate passed a redistricting reform bill Wednesday that had been dramatically changed the day before, drawing fire from anti-gerrymandering advocates who had turned against legislation they helped craft.

The bill, approved 35-14 largely along party lines, would ask voters whether to amend the state constitution to have political district boundaries drawn by a citizens' commission, rather than lawmakers. Proposals had been debated for months, but Republicans added an amendment Tuesday that would put an additional proposal to voters: Should state appellate judges, including Supreme Court justices, be elected from regional districts instead of statewide?

With the amendment, the redistricting reform bill, SB22, became unpalatable to advocates, and some Democrats called the amendment a "poison pill" meant to kill the bill — and activists' attempts at change.

"What we have now is a hijacked concept … that utilized the energy and the commitment of individuals to try to make a difference," State Sen. Vincent Hughes (D., Philadelphia) said on the Senate floor.

He and others accused Republicans of attempting to strike back at the Democratic-majority Pennsylvania Supreme Court, which in January overturned the state's congressional map as a partisan gerrymander.

"The Republicans have blinders on," Senate Minority Leader Jay Costa (D., Allegheny) said after the vote Wednesday. "They are so intent on taking steps to retaliate against our appellate courts that they don't care."

He said the judicial districting proposal "jeopardizes" the chances of enacting redistricting reform; Senate Democrats will appeal to the House to remove the amendment, pass the rest of the bill, and send it back to the Senate for final approval.

>> READ MORE: Anti-gerrymandering bill amended by Pa. Senate GOP; Democrats call it 'poison pill'

Republican leaders say the measure was meant to ensure "geographic diversity." State Sen. Ryan Aument (R., Lancaster), who introduced the amendment, said regional districts would apply the principle of "one person, one vote" — which requires equal populations in election districts — to the judicial system. Many appellate judges have hailed from Philadelphia and Allegheny Counties, Republicans said, including five of the seven current Supreme Court justices.

Aument rejected the "poison pill" idea and said he did not see a need for hearings on the proposal to create judicial districts.

"It was interesting as I was listening to the debate that there was very little disagreement with the concept that I was discussing," Aument said. "In fact, a number of members made the point of saying that they thought the regional approach to judicial districts made a lot of sense and required further review. So a lot of the debate [Tuesday] was really around motive that just frankly wasn't true."

State Sen. Anthony Williams (D., Philadelphia) compared the recast bill to an unwelcome present. "It's the same feeling as a little kid at Christmas who expects a kitten, and they open up that box and out pops a cougar. A cougar is not the same thing, no it's not," he said. "The Eagles, the Cowboys — not quite the same thing. Redrawing lines and putting in lines — not quite the same thing."

Two Democrats, Andrew Dinniman of Chester County and Lisa Boscola of Lehigh County, voted for the bill. Both said they were doing so because it improved congressional and legislative redistricting process, not because they supported the judicial district proposal.

"I would have preferred the pristine version," Boscola said on the floor.

Wednesday's vote sends the bill, with Aument's amendment and other changes, to the Republican-controlled House. Because it would amend the state constitution, the bill must pass both the House and Senate in the exact same form during two consecutive legislative sessions before going to voters to approve or reject. Proposed amendments do not go to the governor.

"We're very hopeful that the House will pick it up," said Senate Majority Leader Jake Corman (R., Centre). "We think it's crucial that this gets done."

The amendments are contained in one bill but would appear as two separate questions on the ballot, Senate officials said. One would ask whether a commission should be established to draw political maps, and the other would ask whether districts should be set up for judicial elections.

If both pass, the independent commission would also draw the lines for judicial districts from which judges would be selected. To affect the next redrawing of election lines, which would occur in 2021, the bill would need to pass the legislature for the first time by early next month and then again next session.

The future of the legislation could depend on which committee it is sent to. Most redistricting bills have gone through the House State Government Committee, where they have stalled or been gutted by State Rep. Daryl Metcalfe (R., Butler). Recently, though, House Speaker Mike Turzai (R., Allegheny) has referred bills to the House Rules Committee, which is chaired by Majority Leader Dave Reed, who himself introduced a proposal.

Spokesmen for Republican leaders did not respond to requests for comment about which committee will receive SB22.

Activists said they would fight in the House and would make gerrymandering a campaign issue in the November election, highlighting senators who voted for Aument's amendment.