Because of an editing error, a report Tuesday incorrectly stated that all 19 members of a group of Chicago suburbanites supported President Reagan after watching the second presidential debate Sunday night. Reagan won back the unequivocal support of group members who had once supported him but had begun to question his qualifications after the first debate. Other members who had supported Walter F. Mondale before the second debate continued to do so.

On Sunday night, President Reagan's voters came home.

They moved almost as one, this small group of middle-class Republicans, Democrats and independents who two weeks ago found their faith in the president unexpectedly shaken by his first debate with Walter F. Mondale. It had left them with doubts about Reagan's age, competence and command -- and with new respect for his Democratic challenger.

But after watching the second presidential debate of 1984 in the home of Susan and Michael Talbot Sunday night, the faith -- and votes -- of these 19 Chicago suburbanites were restored to the Reagan column without reservation.

The debate marked the third time The Washington Post had assembled the group during the campaign; previously it had gathered for the first debate Oct. 7 and reviewed a week of televised ads and campaign news coverage. The group is in no way a scientific sample of the electorate nationwide.

Viewed from the Talbots' family room, front-runner Reagan seemed to have performed well enough to guarantee his lock on the presidency for another four years, even though his responses and his record were not without flaws. And Mondale, after a strong beginning, seemed to put himself on automatic pilot and droned on unconvincingly. He left his supporters in the room disappointed and gave those leaning to Reagan no new reason to abandon their leader, who entered the debate still well ahead in the polls.

After Reagan's performance, Sanford Johnson, Bud Cherry, Frank DeFranze, Monty Clark and Morrie Oldham are back solidly in the president's fold.

The only note of cheer for Mondale is that the gender gap cuts a wide swath through Hanover Park. Dian Johnson, Judy Cherry and Mary DeFranze remain solidly for Mondale -- even more solidly than they were before. Their concerns about Reagan's lack of accomplishment in arms control, his "Star Wars" space defense plan and his policy in Lebanon solidified their opposition to the candidate whom their husbands were ready to rally behind on Sunday night.

According to Mondale senior adviser Richard Leone, the former vice president had come into the debate aiming for a specific group of voters: people who, after the first debate, either had new doubts about Reagan's competence or who viewed Mondale more favorably but were still not ready to declare their support.

Everyone in the group who fit that description wound up moving more solidly behind Reagan by the end of the debate.

"I thought Reagan did much better than in the last debate," said Sanford Johnson, a Republican marketing specialist who had left the first debate with strong misgivings. "He seemed more relaxed, more well rested . . . . Listening to Walter Mondale, I didn't find any new ideas or significantly different ideas that he was proposing . . . that Ronald Reagan has not either attempted to do or has proposed to do." At the end of the debate, Johnson cast his ballot for Reagan -- without the question mark that accompanied it two weeks ago.

Oldham, an accountant who is an independent, said he felt more comfortable now about voting for Reagan because he believes the president will be reluctant to raise taxes. After the first debate, Oldham said he had doubts about Reagan's age, his competence, his ties to the Moral Majority and his social agenda. "As I got farther away from that last debate, my doubts didn't seem as important as they were," he said. "Had Reagan fallen on his face, hemmed and hawed in his answers, . . . I think I would've been really worried."

Democrat Frank DeFranze, a steamfitter who voted for Reagan in 1980, had said he had doubts about Reagan and was only leaning toward him at the outset of the debate. But by the end of it his support was unequivocal. "I think the Reagan administration's performance has left the Mondale people very little ground," he said. "They're very aggressive. I think that's what was needed after the last administration."

Those who came as Mondale supporters volunteered that Reagan had performed far better than they would have liked. "Reagan seemed more up on what he was talking about, more up on foreign policy," said Michael Talbot, a Mondale backer and a Democrat who runs a small truck-parts business. "But some points Mondale made about him not knowing what was going on hit home." He said he thought Reagan looked "foolish" in the controversy over the CIA manual that instructed rebels in Nicaragua in the art of assassination and subversion.

His wife, Susan, a Mondale supporter who keeps the books for the family's business, said she was disappointed that Mondale did not counter Reagan directly and make clear just what arms control agreements with the Soviets can be verified. She noted that Mondale's running mate, Geraldine A. Ferraro, had also seemed uncertain on that point in her recent debate. "She got cagey and said, 'Well, I can't disclose those secrets,' " Susan Talbot said. "I still don't know."

Those who returned to the Reagan fold were willing to overlook the lack of success on arms control and their differences over his foreign policies as they championed Reagan's economic approach. "Things like that happen," Bud Cherry said of the controversies over Nicaragua and Lebanon. "A president can't be on top of everything."

His wife, Judy, saw things from a different perspective. "I can see that things are better economically ," she said. "But I am stronger for Mondale now because of the one point I have been waiting to hear them talk about, and that's the nuclear thing. The whole Star Wars thing. It makes no sense to me to keep escalating this thing."

With the debates over, and just two weeks of campaigning left, the dilemma for Mondale is how to win the support of Monty Clark. He remains on paper the sort of voter Mondale had to have: a former president of the local teachers' union whose national federation has endorsed Mondale, a Democrat who twice voted for the Carter-Mondale ticket, a thoughtful man who has voiced serious doubts about Reagan's social policies and Lebanon decisions and who believes the Star Wars plan is "a pipedream -- it could precipitate a war."

But on Sunday night he cast his sample ballot for Reagan. "In the final analysis, we must be strong internally," he said. "And to do that we need a strong economy . . . . We need three or four years of stability."