An unusually diverse coalition, ranging from divorcees to nuns, poor people to defense contractors and women's groups to tobacco companies, called yesterday for passage of the Senate Finance Committee's tax-overhaul bill.

The coalition, named "15/27/35" after the bill's low tax rates, presented itself at a Capitol Hill news conference as proof that the committee proposal to wipe out many deductions and slash tax rates has won wide grass-roots support.

It came forward at the urging of committee staffers as scores of businesses and groups mounted lobbying campaigns to amend and possibly unravel the bill when it comes to the Senate floor in June.

The coalition vowed to withdraw its support if the bill is changed to include higher tax rates, new taxes or fewer benefits to low-income taxpayers.

The group -- spanning the League of Women Voters, McDonnell Douglas Corp., the Irish Distillers Group, the National Coalition of American Nuns and others -- also includes Washington real estate developer Oliver T. Carr, who announced that he was breaking with organized real estate lobbies, which vociferously oppose the bill.

"I understand the real estate industry [says that it] is seriously threatened by the proposed revisions, and I'm here to tell you that's incorrect," Carr said. "We should be building space to meet people's needs, not to meet the needs of people buying and selling tax shelters."

Sens. John C. Danforth (R-Mo.), Bill Bradley (D-N.J.) and John H. Chafee (R-R.I.) warned the group that the tax bill is extremely vulnerable because almost any significant amendment could destroy its balance of benefits to low-income Americans. They said only a determined lobbying campaign by supporters can prevent this.

"Our constituents are going to be lining up to see us . . . asking for amendments," Danforth said. "Politicians want to be responsive to our constituents. We want to say yes."

Remarking on the national drive to save deductions for all Individual Retirement Accounts, Danforth said: "I would hope people won't get so revved up about the issue of IRAs" that they would undo the bill.