Senate Finance Chairman Max Baucus (D-Mont.) has joined the fray between Finance ranking member Chuck Grassley (R-Iowa) and a group of televangelists whose allegedly lavish lifestyles caught Grassley’s attention.

Baucus added his signature to letters that Grassley sent on Tuesday to four ministries, setting a March 31 deadline for compliance with Grassley’s earlier requests for financial information and holding out the threat of issuing subpoenas.

Three of the ministries have suggested they do not plan to provide the Finance Committee with detailed financial data about their expenses, donations and business transactions.

As ranking member, Grassley cannot subpoena the churches without Baucus’ support as chairman. Thus, the nod of the Montana Democrat is crucial if the feud escalates.

No matter who chairs the powerful Finance Committee, Baucus and Grassley work closely together, and one aide described Baucus’ signing onto the letter as evidence that he was “backing up” Grassley’s tactics.

The three church leaders who have not cooperated thus far are: Kenneth and Gloria Copeland of Kenneth Copeland Ministries based in Newark, Texas; Creflo and Taffi Dollar of World Changers Church International in College Park, Ga.; and Eddie L. Long of New Birth Missionary Baptist Church in Lithonia, Ga.

“The Committee continues to hope that mutually respectful discussions will enable the Committee to obtain the requested information without resorting to compulsory process,” the letters to the three churches say.

“Therefore, as Chairman and Ranking Member of the Committee on Finance, we are affording you another opportunity to send the information requested by Senator Grassley.”

According to Grassley’s office, two churches have substantially cooperated: Joyce Meyer Ministries in Fenton, Mo. and Benny Hinn’s Grapevine, Texas-based World Healing Ministries.

Randy and Paula White of Without Walls International Church based in Tampa, Fla., have indicated to committee staff that they intend to cooperate, but have not yet done so. A March 11 letter to the Whites said the Senators “look forward to mutually respectful discussions.”

Sparking some complaints to his office, Grassley started the probe into six churches’ tax-exempt status by sending letters requesting financial data on Nov. 5.

Grassley has described the probe as part of a series of investigations into tax-exempt organizations, which have also targeted The Nature Conservancy, the Smithsonian and the Red Cross.

But Copeland has preached from the pulpit that the information sought by Grassley belongs to God, not the Senate, and that he will never on pain of death turn over church financial records to the Senator. The Rev. Dollar has said Grassley will have to subpoena his church if he expects to get the records.

Copeland and Dollar argue that they do not want to make proprietary church information public by handing it over to the lawmakers. But Grassley says he “recognizes the concerns regarding privacy” and has said he would “work with” the churches to keep select information private.

The probe, say some in the evangelical community, presents a problem for Republicans who rely on evangelical voters during an election year. They question whether Grassley, a Baptist, is exhibiting religious bias by examining only Pentecostal churches with charismatic leaders. Grassley denies that charge.

Most of the churches under fire preach a “Prosperity Gospel” that says God encourages the acquisition of earthly riches.

None of the churches contacted Wednesday responded to requests for comment on the second round of letters.