MANCHESTER, N.H., FEB. 10 -- Rep. Richard A. Gephardt (D-Mo.), riding a made-in-Iowa "bounce" in the latest Washington Post-ABC News poll of New Hampshire Democratic voters, took the fight on international trade today to the state's front-runner, Massachusetts Gov. Michael S. Dukakis. But Gephardt found himself under attack on nuclear safety policies from Sen. Paul Simon (D-Ill.), his rival in a second-place battle for survival.

The increasingly sharp volleying came as Gephardt and Simon cut short their campaigning for next Tuesday's primary in order to restock their depleted treasuries with fund-raisers in Washington and New York.

Meanwhile, the Post-ABC poll of 403 likely Democratic voters, taken Tuesday night, showed Gephardt getting a much larger boost from his first-place finish in Monday night's Iowa caucuses than Simon got from finishing second. Gephardt appeared to move past Simon into second place here, and Dukakis lost half of his 30-point lead overnight.

The Tuesday survey showed Dukakis, who finished third in Iowa, at 37 percent, Gephardt at 21 percent and Simon at 17 percent. A Post-ABC poll of New Hampshire voters taken Feb. 1-7 had given Dukakis 43, Simon 13 and Gephardt 12. So Dukakis lost 6 points, Gephardt gained 9 and Simon gained 4.

The poll showed Dukakis and Gephardt are roughly splitting the predominantly moderate Democrats, while Dukakis and Simon claim the bulk of the liberal vote.

As usual, the trailing candidates in Iowa remain far back here, with Sen. Albert Gore Jr. of Tennessee and Jesse L. Jackson at 5 percent, and former Colorado senator Gary Hart and former Arizona governor Bruce Babbitt at 4 percent.

Gephardt, while calling Dukakis "the far-and-away favorite" in next Tuesday's voting, seized the aggressor's role in a news conference outside one of the senior citizens' centers he visited here.

Standing without a coat in an icy wind, the red-haired congressman accused his rival of shifting positions on trade policy depending on where he was campaigning.

"When Gov. Dukakis was in Iowa, he was talking about trade policy and he sounded a lot like me," said Gephardt, author of a provision in the House-passed trade bill for retaliatory tariffs if nations with persistent trade surpluses do not lower their barriers to American imports. "He sounded like we had to get tough on trade policy and he had very little criticism . . . about my trade policy. Frankly, I think he had a conversion when he got on the plane to come out here to New Hampshire."

Unlike Iowa, which has seen layoffs and shutdowns in major industrial plants with foreign competition, this state has a prospering high-tech industry, many of whose companies have flourishing overseas markets.

Just an hour before Gephardt unloaded on Dukakis, the governor had made an appearance at St. Anselm's College in nearby Goffstown, accompanied by An Wang, the head of Wang Industries of Lowell, Mass., a major employer of New Hampshire residents and a major exporter.

There, Dukakis expressed confidence that American firms and workers could "out-produce, out-market, out-invent and out-compete" anyone, adding that "the real choice has nothing to do with the debate between free trade and protectionism . . . . The real question is whether we circle our wagons where we are, or whether we move forward with energy and confidence . . . . "

Told of Gephardt's charge that he has changed his view since leaving Iowa, Dukakis said, "People should just look at the tape of our August debate."

In that debate at Drake University in Des Moines, and in many Iowa appearances over the past six months, Dukakis has assailed the Gephardt trade amendment, saying "it has the potential for setting off a trade war" and arguing that "the president already has all the authority he needs to deal with unfair trade practices."

While Gephardt was baiting Dukakis, he found himself on the defensive with Simon, who took his campaign to a site within camera range of the Seabrook nuclear plant and accused the Missouri congressman of changing his mind on the sensitive nuclear power issue.

Gephardt, Simon said, opposed a 1979 bill that would have limited the Nuclear Regulatory Commission's power to grant licenses in states that have no evacuation plan.

"He now professes to be a champion of nuclear safety," said Simon, who, like the other six Democratic candidates, opposes the opening of the Seabrook facility. The plant remains dormant, in part because Dukakis refused approval of an evacuation plan for the plant, which is within 10 miles of the Massachusetts border.

Simon aides said that his decision to go after Gephardt on his so-called flip-flops is part of a strategy to challenge the Iowa winner while ceding first place to Dukakis.

Citing other changes by Gephardt on the Equal Rights Amendment, abortion and tax reform, Simon said, "The American people have had a hard time knowing where he is going to go. They don't have a hard time knowing where Paul Simon is going to go."

"Paul knows better than that," Gephardt said in reply. "I think he's listening to advisers who are telling him he's got to say some things he doesn't really believe. I have had a strong record on environmental and nuclear issues, and I think he knows that."

Returning fire, Gephardt said, "I don't want him questioning motives. I didn't question his motives when he came out for Ronald Reagan's balanced-budget amendment, Ronald Reagan's line-item veto, for Ronald Reagan's subminimum wage" for youths. "We may disagree on those issues but I would never question his motives."

Polling editor Richard Morin and polling analyst Kenneth E. John contributed to this report.