The offensive mounted by the Democrats comes two weeks before Clinton is set to make her first public testimony before the committee.
They want everyone watching what Republicans ask, and anything that seems to be an overreach could give Democrats exactly the fodder they need to cement their claims that the issue is a manufactured crisis with a purely political purpose.
The top Democrat on the panel, Rep. Elijah Cummings, railed on Tuesday against what he called "an unethical abuse of millions of taxpayer dollars and a crass assault on the memories of the four Americans who died," adding, "I believe it should be halted immediately."
On Tuesday evening, Rep. Louise Slaughter, ranking member of the House Rules Committee, offered an amendment to the Republican bill creating a select committee to investigate Planned Parenthood that would replace the language of the bill with alternative text abolishing the Benghazi committee, according to her spokesman. The amendment was rejected along party lines.
The No. 2 House Democrat, Steny Hoyer, suggested Democrats on the committee may cease their participation in the panel after Clinton's testimony on October 22.
"This committee is a discredit to the House of Representatives and ought to be disbanded," Hoyer told reporters Tuesday. "I don't think this was serious from the beginning: We alleged that its objective was what now Congressman McCarthy admitted on national television it was. So whether we participate beyond the hearing has not been decided."
But Cummings said he's not personally ready to pull out just yet.
"I am not naïve in thinking Republicans will cease their political attacks on Secretary Clinton, which is why I will be in that room defending the truth," he said in an email to CNN.
If House Democrats pull out of the select committee after the former secretary of state testifies later this month, the work would be left to the GOP members of the panel and give Clinton's camp more fodder to dismiss it as a partisan enterprise.
Before McCarthy's comments triggered a backlash, the Republican members on the Benghazi panel began crafting a strategy for the high-profile hearing with Clinton. According to a source familiar with the discussions, GOP members want the primary focus to be on questions about the attacks in Benghazi that killed four Americans and the government's response to them, not the latest back and forth over Clinton's email server.
McCarthy's comments under scrutiny
The Democrats are seizing on McCarthy's fumble last week -- when he made comments about the power of House committees to advance the Republican agenda and implied that the Benghazi Committee was behind Clinton's trouble in the 2016 presidential race.
"Everybody thought Hillary Clinton was unbeatable, right?" McCarthy said on Fox News. "But we put together a Benghazi special committee, a select committee. What are her numbers today? Her numbers are dropping. Why? Because she's untrustable. But no one would have known any of that had happened had we not fought."
House Minority Leader Nancy Pelosi first floated the idea of Democrats pulling out last week in a press conference, when she said her party's participation would depend on "how serious" Republicans are.
On Tuesday, Pelosi's office declined to comment on any future steps Democrats might take in terms of their participation in the select committee's proceedings, but did not rule it out.
The left-leaning editorial board of The New York Times on Wednesday published an editorial
calling for the committee to be disbanded or renamed "the Inquisition of Hillary Rodham Clinton" -- which the House Democratic leader's office quickly sent around to reporters.
Republicans have seized on the remarks along with Democrats to criticize McCarthy, who is waging a campaign to replace House Speaker John Boehner. He is facing an extra challenge from his own party, in the form of Utah Rep. Jason Chaffetz, after his remarks roiled the leadership race.
McCarthy released his own statement Tuesday defending the work of the committee.
"The mission of the Select Committee on Benghazi is to find the truth -- period," McCarthy said.
A spokesman for the majority leader did not respond to requests for comment, pointing to previously released statements.
With McCarthy on his back foot, Democrats are using every opportunity to turn the comments against Republicans.
On Monday, the Clinton campaign released a 30-second ad to air on cable networks that uses McCarthy's comments and slams the $4.5 million the House panel has spent.
In the ad, the narrator says: "The Republicans have spent millions attacking Hillary because she's fighting for everything they oppose. From affordable health care to equal pay, she'll never stop fighting for you and the Republicans know it."
The day before, Democrats on the Benghazi committee sent a letter to the panel chairman, South Carolina Rep. Trey Gowdy, releasing some excerpts of closed testimony by Clinton's top aide Cheryl Mills and threatening to make the entire interview public in what they called an effort to "correct the public record" after a series of selective leaks by Republicans.
Cummings said Republicans themselves are to blame -- and McCarthy has only publicly confirmed what the panel's Democratic members have long felt as the committee's leaks damaged Clinton.
"When you just put out some emails and there is no context -- he started this," Cummings said. "And so what we're doing is clearing the record."
The committee's communications director, Jamal Ware, accused the Democrats of revealing their "nakedly political motivation" and accused them of "running a protection effort for the former Secretary."
Ware called Democratic threats to walk away from the committee after Clinton testifies "clear evidence" of "political duplicity."
"The Democrats only care about providing cover for Clinton, and have never attempted to contribute substantively to the Committee's work," Ware said. "Regardless of whether the Democrats are present or not, the Committee will treat all witnesses fairly. Beyond that, the majority remains focused on gathering facts and cannot concern itself with the Democrats' political scheming."