Del. Walter E. Fauntroy, the only leading District politician campaigning against the statehood initiative on the Nov. 4 ballot, predicted yesterday that the measure would be approved by voters, thereby setting in motion a long and almost certainly controversial process that could make the nation's capital the 51st state.

"I think it's going to pass," Fauntroy told reporters. "Everybody's against sin and for motherhood." He acknowledged that widespread popular support for home rule is likely to outweigh the specifics of the statehood measure.

Fauntroy's statement, along with the absence of a vigorous negative lobby of the kind that defeated a legalized gambling referendum in May, was the strongest indication yet that the statehood initiative would pass. Approval by a simple majority of those persons voting on the referendum is all that is required.

Fauntroy made his remarks after a forum at the downtown campus of the University of the District of Columbia. During the two-hour session, Fauntroy told students, faculty members and a number of proponents of the measure that a vote for statehood would make more difficult his own continuing efforts on behalf of the now-stalled D.C. Voting Rights Amendment to the U.S. Constitution.

Although Fauntroy maintained throughout the forum that he believed the statehood idea was an unweildy one that would quickly become bogged down in technicalities, he all but acknowledged that the initiative places him in an awkward position.

On the one hand, he is firmly committed to the Voting Rights Amendment, which he shepherded through Congress, as the means for the District to obtain full representation on Capitol Hill; on the other, no District politician can comfortably take a position against any measure that might advance the cause of home rule.

"I'm sorry these people have got me here arguing with the statehood people," Fauntroy said. "We're all for self-determination." At another point during the forum, he said, somewhat unconvincingly, "Let me assure you that I'm not going to spend a minute's time campaigning against statehood," and promised to give his news on the measure only when asked.

The measure would by no means insure that the District would become the 51st state. Rather, it would begin a lengthy process that could lead to statehood if D.C. residents and the Congress give a number of subsequent votes of approval.

Residents of the 50th state, Hawaii, first voted to apply for statehood in 1940. But it took 19 years until Congress voted to admit Hawaii as a state in 1959.

If the Nov. 4 initiative is passed, D.C. voters will have to go to the polls again to call for a constitutional convention and elect 45 delegates to that convention. After the body writes a state constitution, the mayor must submit the document to the voters for approval. If the new constitution is approved, it is submitted to Congress. A simple majority vote of both houses would make the District a state.

D.C. statehood would not have to be approved by a two-thirds majority of the state legislatures -- a provision that has placed the full voting rights drive in grave jeopardy. Only nine of the required states have approved the amendmeent during the first two years of the seven-year period allowed for ratification.

Virtually all major District political figures except Fauntroy are backing the statehood initiative. At a recent press conference, Mayor Marion Barry called support of the measure "fundamental." But few officials are taking any active role in pushig the measure, and most believe it will pass with or without their help.

The prostatehood positio at yesterday's UDC forum was taken by Sam Smith, a longtime activist with the Statehood Party who publishes the D.C. Gazette, one of the city's leading alternative newspapers.

"The message is going to be, if statehood is defeated this time around, that we're happy with the way things are," Smith said. "In this very unpleasant election year there is at least one vote you can be proud of."

Smith argued that the essential issue was one of D.C. residents obtaining the same status as other Americans, while acknowledging that the statehood measure would not of itself solve the District's pressing social and financial problems.

At several points, Smith sharply attacked Fauntroy's contention that the best way to win voting representation for the District in the Senate and the House of Representatives is through the Voting Rights Amendment.

"All of Del. Fauntroy's arguments seem to hinge on his tactical prescience," Smith said. "I don't think as a tactician he's naturally someone we ought to follow."

But Fauntroy's chief political talent is as a homegrown Baptist minister and skilled and flexible orator who shifts easily from high-sounding polysylabic verbiage to down-in-the-streets straight talk. He argued that statehood would cloud the issue of the federal payment, the annual sum Congress pays the District to make up for lost tax revenues on federal property and other costs the city government incurs by virtue of being the nation's capital. Statehood would not work without firm assurances that the payment would continue, he argued.

"It's like the Indians and the reservations," he said. "The government said you can have complete self-determination after we kill the buffalo. Well, if the government is going to play cowboys, I'm not going to play Indians."

Smith contended that while the federal payment issue may be cloudier under statehood, the District would without doubt have the authority to impose a commuter tax -- long sought as a way of increasing revenues.

In addition to the statehood question, a referendum to legalize some forms of gambling, the nonvoting delegate's seat in Congress, six seats on the City Council and president of the United States will also be on the ballot 13 days from today.