The fight over a toxic chemical bill announced two weeks before Sen. Frank R. Lautenberg’s death has gotten deeply personal, with Lautenberg’s widow making calls to Sen. Barbara Boxer, chairwoman of the Senate Environment and Public Works Committee, to advocate for the legislation, according to multiple sources familiar with the talks.

Boxer has concerns with the chemical safety legislation, revolving largely around potential pre-emption of California law and another provision that troubles trial lawyers, as CQ Roll Call reported Tuesday. EPW committee Democrats are scheduled to meet with trial lawyers Thursday in an emergency gathering to discuss the bipartisan bill brokered by Lautenberg and Republican David Vitter of Louisiana, with the help of Joe Manchin III of West Virginia.

But the personal nature of the lobbying on the bill from Boxer and her committee staff director, Bettina Poirier, has created an uncomfortable situation for other Democrats on the panel, many of whom are afraid to get in the middle of an internal fight between a chairman and a deceased former colleague.

Multiple sources confirmed that Bonnie Englebardt Lautenberg has reached out to Boxer, whom she considers a friend, to discuss the legislation. When CQ Roll Call asked Boxer in an interview if she had communicated with members of the Lautenberg family about the bill, the California Democrat said, “My relationship with the Lautenberg family is private.” Boxer’s office declined to comment further.

Manchin told CQ Roll Call he briefly discussed the future of the bill with Englebardt Lautenberg at her husband’s funeral.

Questions from Boxer and her staff about whether the late senator was mentally able to sign off on the bill have created the most tension, especially for allies of the legislation and Lautenberg staffers, according to multiple aides and members involved in the talks.

The bill would implement the first changes in chemical law in nearly 40 years and it was supposed to be the capstone of a long legislative career in which Lautenberg had pursued new federal standards for toxic chemicals.

The rhetoric over the bill became more personal in the days following the New Jersey Democrat’s June 3 death, exemplified by an emotional email, obtained by CQ Roll Call, that was sent June 13 by a Lautenberg aide.

A coalition of environmental groups — including the Environmental Working Group, Friends of the Earth and others — had issued a statement against the Lautenberg-Vitter bill. The statement said the compromise was “largely authored by Louisiana Senator David Vitter” and that the best way to “honor” Lautenberg would be to pass a stronger bill.

Supporters of the legislation say Poirier’s lobbying influenced the outside environmental groups to take this position.

The Lautenberg staffer’s email to the environmental groups, which also was sent to legislative aides of the nine Democratic co-sponsors of the bill, stated that the groups’ original remarks were “deeply insulting” and said they owed “a public apology to his widow and family.”

“You have crossed a serious line in your last statement that you circulated this morning. The highlighted sentences below presume that you know more about what Senator Lautenberg wanted than he did himself. … It is pretty clear what he wanted to do and what he thought his legacy should be. Your statement is fundamentally insulting to him, his memory and his family — moreover a statement released less than a week after he was buried,” the staffer’s email read.

It continued: “I would step back and take a moment to think through your message on this and send an apology and a retraction of this part of your statement. I know most of you personally and am surprised that you would put this out — it’s not in keeping with your characters. It is a new low and deeply insulting to a man who some of you worked for and championed causes and legislation that you supported for nearly 30 years. In my view, a public apology to his widow and family is in order.”

Lautenberg’s office later confirmed that it received an apology from the environmental coalition.

The back-and-forth with the outside groups was a microcosm for the larger battle over the approach Boxer’s staff took to squashing the bipartisan bill, according to a source familiar with the events. By lobbying these groups against the bill, this source said, Boxer’s staff could then arm the chairwoman with a narrative that environmental groups opposed it on the grounds that Lautenberg did not sign off on his own agreement.

Manchin — who helped bridge the gaps between Lautenberg and Vitter — had a heated conversation on the Senate floor with Boxer about the bill, with Boxer challenging the contents of the legislation and accusing the sponsors of not knowing what they were signing off on, according to a source with knowledge of the exchange. A second source confirmed the exchange.

Both Manchin and Boxer said they have a good relationship.

“We may have a difference of approach of where we’re coming from but we’ve always been able to work, no problem at all,” Manchin said. “It’s never been contentious.”

Boxer said in a statement: “Not only are Joe Manchin and I very good friends, we are working together and he will be one of the leadoff witnesses at our hearing.”

Manchin said he was not previously aware of an invitation to speak at the hearing, which Boxer said would happen in July.

Multiple sources tracking the legislation said that Sen. Kirsten Gillibrand, D-N.Y., had agreed to champion the legislation in Lautenberg’s absence; neither she nor her office were available for comment Wednesday. Gillibrand is both a member of the EPW committee and a co-sponsor of the Lautenberg-Vitter bill.

Vitter also declined to comment, directing CQ Roll Call to a press aide.

Multiple sources close to the bill say there is an easy legislative fix to the private causes of action issue, which will be addressed in Thursday’s meeting of committee Democrats with trial lawyers and other environmental groups.

This report has been updated to clarify that a broad environmental coalition wrote the statement opposing the Lautenberg-Vitter bill.