BOSTON, SEPT. 13 -- Forty-eight hours after the final debate of the Massachusetts gubernatorial primary campaign, the battle for the Democratic nomination seems over -- and the fight for the GOP nomination freshly in doubt. The net effect of the tumultuous period has been a sharp increase in the possibility that a Republican may win the governorship of this state for the first time in 20 years.

A firestorm of controversy over the latest "shocker" from Boston University president-on-leave John H. Silber has seemingly doomed his challenge to former state attorney general Francis X. Bellotti for the Democratic nomination. But the way Bellotti sweated and stumbled his way through the final Democratic debate, carried live by TV stations across the state just before President Bush's televised address to Congress Tuesday, dismayed Democrats looking ahead to the November election.

A poll published today in the Boston Globe confirmed street talk that former U.S. attorney William Weld's saturation-level, self-financed TV ad campaign may have virtually erased the year-long lead state House Minority Leader Steven Pierce has held in the fight for the Republican nomination, which will also be settled in Tuesday's primary election.

Democrats who felt Pierce's anti-abortion stance would help their nominee in November now confront the possibility that the abortion rights issue could disappear if Weld is the GOP candidate -- leaving the debate focused squarely on who can best clean up the fiscal mess left by retiring Gov. Michael S. Dukakis (D).

Bellotti's prospects had been boosted by Lt. Gov. Evelyn Murphy's (D) decision Monday to withdraw from the race and endorse him. But Bellotti appeared anything but confident during the debate.

For most of the debate, Silber was everything Bellotti was not -- articulate, calm and collected, even managing a few self-deprecating comments designed to defuse his reputation for arrogance. But a few minutes before the end, Silber delivered another of the "shockers" that have marked his first bid for public office.

Asked why he had not made a speech on crime in the predominantly black Boston neighborhoods of Roxbury, Mattapan and Dorchester, Silber said, "Well, I will tell you something about that area. There is no point in my making a speech on crime control to a bunch of addicts."

A councilman from the minority neighborhood confronted Silber before the candidate even left the debate site. Late Tuesday night and early Wednesday, Silber toured TV and radio studios, trying as he has so often in the campaign, to stop the bleeding from a self-inflicted wound. Later Wednesday, at a hastily scheduled event in Roxbury, he said, "I deeply regret the confusion" caused by his comment, but he was virtually driven from the scene by hecklers. An overnight poll published this morning in the Globe showed him trailing Bellotti, 54 to 31 percent.

Silber represented the last hope that the Democrats would have a nominee untainted by close personal and political ties to the unpopular Dukakis administration. But when asked early in the debate about his penchant for controversy, the Texas-born educator sounded almost resigned to defeat.

"I have nothing to apologize for except that I have been a philosopher and teacher most of my life," he said. "I didn't realize I had a gift for very sensational sound bites. . . I'm not a professional politician. It's amateur hour for me."

But most of the night, he looked and sounded much better than prospective nominee Bellotti. A campaign spokeswoman said Bellotti "is a person who just happens to sweat a lot, and there's only so much you can do to control it."

The 67-year-old candidate was particularly halting in his summation. Campaign aides said he had tried to memorize the closer, but then decided to refer to notes and became confused.

All this had Republicans cheering. When Weld was asked at a news conference Wednesday if he saw a candidate in the Democratic debate "you'd prefer to run against," he replied, "I saw two of them."

Until the last two weeks, Pierce seemed to have the GOP nomination cinched. But the Globe's poll this morning showed his lead down to only 4 points.

Special correspondent Christopher B. Daly contributed to this report.