With advocates for the homeless divided on the measure's impact, District of Columbia voters will decide Tuesday whether to approve an initiative that would require the city to provide "adequate overnight shelter" for what could amount to thousands of people.

Approval of the ballot question, Initiative 17, would make the District the first place in the nation to guarantee shelter as a right by referendum.

Proponents of the initiative, including its original sponsor, the Community for Creative Non-Violence (CCNV), and numerous labor, church and mental health groups, argue that providing overnight shelter for the city's growing numbers of homeless street people is a necessary, just and civilized response to a tragic problem.

"We think the city could do a lot better with the money it spends for shelters than it is doing now," said Stephen O'Neil, a CCNV member and a leader of the pro-initiative forces.

But opponents of the ballot measure, including the District government and a group of churches and private community organizations known as the Coalition for the Homeless, warn that passage of the initiative would result in costly "warehousing" of up to an estimated 15,000 people who would seek shelter if the city was required to provide it.

"To shelter the homeless is not just good, it's a moral responsibility," said the Rev. John Steinbruck, senior pastor at Luther Place Memorial Church and chairman of the Mayor's Task Force on the Homeless. "But when you get into rights to shelter, it presents a problem."

The financially beleaguered District government sued its Board of Elections and Ethics last month and went to court in an unsuccessful attempt to exclude the initiative from the ballot. City agencies this week, in a move cleared with the corporation counsel's office, distributed "fact sheets" and "position papers" to all District government employes, calling Initiative 17 "unwise legislation" and saying it should be defeated by voters.

If Initiative 17 is approved, however, District officials are set to go back to court to challenge the measure, which they say improperly interferes with the city government's budget process.

At issue, in particular, is the city's concern that implementing the initiative could cost the District government $63 million to build huge, new shelters, which is about $60 million more than the city now spends each year to provide 753 beds for the homeless.

The free shelters, the officials say, would become a "magnet" for homeless people from other jurisdictions, and operating the facilities would divert funds from daytime support programs. There is also concern that the shelters would attract drug addicts, who would seek the free lodging as a way to help support their habits.

In addition, members of the Coalition for the Homeless complain that the initiative ignores the question of the need for comprehensive psychiatric, medical, housing and support services. Without those, they say, a homeless person would remain part of a revolving shelter population.

Proponents of the measure, accusing the city and other opponents of exaggerating its financial impact, insist that the initiative would not force the city to spend more on shelters than it does now. And, pointing to a provision in the initiative that would exclude those who come to the District expressly for free shelter, they reject the notion that D.C. would become inundated with homeless people.

But Steinbruck, who worries that richer suburban jurisdictions will be "off the hook" while black families in the city shoulder new tax burdens, says the provision will be hard to enforce: "How am I to interrogate someone, and do I wish to?"

Though the petition to place the homeless initiative on the ballot garnered a record 32,000 signatures of support, the ballot fight has resulted in a bitter split among church leaders and other shelter care providers. Some, such as Steinbruck, have attacked CCNV, charging that the organization did not consult other shelter operators before setting the ballot measure in motion.

Also, Keary C. Kincannon, executive director of the Coalition for the Homeless, resigned this week, saying he could no longer work for the coalition because he supports the initiative and the coalition does not.

The initiative's backers say they do not claim the measure is the whole answer to the problems of the homeless, just a start.

"It's a question of what it costs to leave people on the streets," said CCNV's O'Neil. "These people -- to get out of the cold -- end up in our hospitals, our mental institutions, our fire stations and our jails."

While the city has predicted it will win a court fight against the initiative, supporters of the measure say they are confident it can withstand any legal challenge. They reject comparisons to the Rhodes Tavern Initiative fight, in which voters two years ago overwhelmingly approved an advisory ballot measure designed to save the historic downtown building -- only to see it torn down this fall after the city went to court to urge the building's demolition.

"We're asking for a law here," said O'Neil. "This is not an advisory initiative."