With legislative leaders confident a bill authorizing an interim U.S. Senate appointee will garner enough votes to pass, the Election Laws Committee collected enough panel votes Wednesday to send the bill to the floor with a positive recommendation.

At least nine of the committee’s 16 members have either returned favorable votes to the panel’s leadership or publicly committed to backing the bill, according to a News Service review. Four of the six senators on the panel are on board, with at least five House members supporting and at least four opposed, according to public statements, direct conversations, or aides’ confirmations of their bosses’ votes.

As speculation mounted about who might fill the late Sen. Edward Kennedy’s seat, lawmakers on both sides of the bill predicted a backlash if Beacon Hill is seen rigging the succession chain at the behest of national Democrats. President Barack Obama’s political operations again pressed supporters Wednesday to flood state legislators’ phone lines with calls of support for legislation authorizing Gov. Deval Patrick to appoint an interim senator.

Sen. Jack Hart, an ally of Senate President Therese Murray, raised alarms Wednesday that the prospective decision by the Legislature, expected as early as Thursday, authorizing the temporary appointee could doom Beacon Hill’s efforts to recover voters’ confidence after a string of corruption scandals.

“The people of Massachusetts, I think, will revolt over this thing if it takes place,” Hart told the News Service, adding that he had voted against the bill in the Election Laws Committee poll open until 11 p.m. Wednesday night.

“This is the possible proverbial straw that might break the camel’s back in terms of the public trust in us,” Hart said.

House allies of Speaker Robert DeLeo said leadership had tabulated enough votes to win, but said vote-counters were uneasy that last-minute changes could undermine the majority vote needed to rewrite the 2004 succession law.

Pointing to reforms on ethics, campaign finance, and transportation the Legislature and Patrick enacted this year in bids to restore public confidence rocked by Hill scandals, Hart said, “And here we are, once again on the precipice of another very controversial decision, and the overwhelming amount of people I have talked to, and have called, have said it amounts to hypocrisy. I call it chicanery.”

Sen. Stephen Buoniconti, who voted against the successful effort to strip then-Gov. Mitt Romney of appointment power in 2004, said he planned to vote in favor of appointment power again, and yes on the bill.

“I am a yes. I was one of the rare Democrats voted for a transitional replacement. I am very consistent,” Buoniconti said, acknowledging that he had to look up his 2004 vote to be sure. “I don’t care about the party. It’s all about having full service in terms of senators.”

Asked about Hart’s criticism of the momentum-gathering push to change the law, Buoniconti said, “It’s hard to disagree.”

“Please call your Massachusetts state representative and state senator right now, and tell them that Gov. Patrick needs to be able to appoint an interim senator to represent us until the special election in January,” wrote John Spears, Massachusetts director of Organizing for America.

A vote on the bill could come as early as Thursday afternoon, when both the Senate and House are scheduled to hold formal sessions. Republican lawmakers could also seek to postpone votes through a variety of parliamentary gambits.

Reps. William Bowles, Stephen “Stat” Smith, and Mark Falzone all confirmed their support for the committee’s endorsement. An aide to Rep. Willie Mae Allen said she supported the bill.

“I’m with leadership,” Smith said.

“I voted to bring that out of committee, and I expect that tomorrow they’re going to be doing a resolution” stating the House and Senate would firmly oppose any appointee running for the seat permanently, Bowles said. Such language was struck from the bill due to constitutional concerns. Bowles said his support for the bill was contingent on the resolution’s passage by the full House.

Opposing the bill in the House are committee members Minority Leader Brad Jones, Reps. Paul Frost, Paul Kujawski, and freshman Brian Ashe.

Ashe (D-Longmeadow) said he voted against recommending the bill, calling it “a bit hypocritical” for Democrats to look to reinstitute appointment power for the governor after stripping it from Romney in 2004.

Ashe said he had received nearly 100 emails on the matter, with “over 90 percent” against rewriting the law.

“My guess is it’ll get out of committee, but I don’t know if it will pass the House,” Ashe said.

Rep. Thomas Golden, the Lowell Democrat, did not respond to messages left at his office and cell, and has previously called himself undecided.

In the Senate, Hart and Sen. Scott Brown voted “ought not to pass.” Sens. Thomas Kennedy, Joan Menard, and Anthony Petruccelli have all said they support the legislation, a redraft of H 656.

That bill was originally written by New Bedford Democratic Rep. Robert Koczera, who wrote in language aimed at guaranteeing that the interim appointee would not seek the seat in a special election. Koczera has said he still prefers that statutory firewall.

The version expected to emerge from committee late Wednesday does not include the firewall to prevent the appointee from running for the permanent job, and calls for any temporary successor to hail from the same party as the seat’s last occupant.