Next week's U.S.-Soviet summit is likely to produce higher poll ratings for President Reagan but a party-splitting dispute among Republicans over the arms-control agreement Soviet leader Mikhail Gorbachev is coming here to sign.

In the short term, Democrats could lose an arms control issue they have used effectively in the past to recruit activists. In the long term, they could gain if fading fears of international conflict focus the voters' concerns even more on economic worries at home.

Of all the 1988 hopefuls, Vice President Bush stands to gain the most from a successful summit, but he and his rivals will all face fresh scrutiny as Americans calculate who is best equipped to sit across the table in future negotiations and try to match Gorbachev's diplomatic dexterity and personal force.

These are some of the conclusions expressed by political figures in both parties interviewed in the last few days by The Washington Post on the possible political fallout of the summit that begins in Washington next week.

From presidential pollster Richard Wirthlin to erstwhile Democratic presidential hopeful Gary Hart, most agreed that this summit -- unlike many in the past -- could turn out to be a signally important political event.

Part of it is the timing -- just at the moment when millions of Americans are beginning to focus on the choices they must make in the next few months as they narrow the field of contenders for Reagan's replacement. "The issue may not last a year," Republican pollster Robert Teeter remarked, "but it could be important in the next 60 to 90 days, which is very important" because it is roughly the span of time in which more than half the states will choose convention delegates.

Adding to the summit's potential is the exceptional curiosity about Gorbachev, a Russian leader viewed favorably by almost as many Americans as think favorably about Reagan, according to the latest Washington Post-ABC News poll. Hart, who spent several hours with him in the Kremlin last last winter, said he expects the Soviet leader to have "a very powerful impact" with his "inquisitive, absorbing" mind and "engaging" personality. "At the very least in the early states," he said, "voters will ask a lot of questions of how the candidates intend to deal with Gorbachev."

The Post-ABC poll showed voters have high expectations of substantial progress from the meeting, based on a strong belief that both leaders genuinely want agreement. Most like what they have heard about the intermediate-range nuclear forces (INF) agreement awaiting signature and believe a second, larger agreement could follow..

"Historically," Wirthlin observed, "summits haven't affected presidential job ratings that much, but this one is unique."

Here are some of the major effects these political figures see if the summit goes off successfully:

On Reagan: "It's got to help Reagan," said former Republican secretary of defense Melvin R. Laird, "and anything that helps Reagan helps the Republican Party." Few disagree. Larry K. Smith, president of the Business Executives for National Security and formerly an arms-control adviser to leading Democratic senators, said, "The survey data clearly shows most Americans tend to be deeply skeptical about Soviet motives but, at the same time, want to do business with them, especially on the nuclear issue. For the past six years, Reagan has emphasized almost exclusively the skepticism and many Democrats emphasized only their desire to do business.

"With the Gorbachev visit, Reagan is moving for the first time to give voice to both themes. He's being the very model of American pragmatism. We ought to give him his due."

On the Republicans: Ironically, the issue has split the Republican candidates badly, with four of the six presidential contenders -- Alexander M. Haig Jr., Pierre S. (Pete) du Pont IV, Jack Kemp and Marion G. (Pat) Robertson -- critical of Reagan's signing the INF agreement and Robert J. Dole holding off his expected endorsement and suggesting he may support some amendments. "It exposes the power of the right wing in the Republican nominating process," Democratic consultant Paul Maslin exulted. Democratic pollster Peter D. Hart said he found "hard to understand why they would play primary-election politics" on an issue where "every poll shows the voters in the general election support the treaty and want arms control."

The internal Republican quarrel will be evident again during the Senate ratification battle, but most observers think it will be an issue in the presidential election only if the GOP "die-hards" manage to defeat or cripple the treaty. But Paul Weyrich, president of the conservative Free Congress Foundation, sees a more lasting danger. "Anticommunism has been one of the greatest themes holding the Reagan coalition together," he said. "It bridges the gap of neoliberals, the religious right and the old right. Once you make anticommunism seem almost out of step with the times, you lower the chances of keeping the coalition intact."

On Bush: "It's a ten-strike for Bush," said Democrat Maslin, and almost everyone agrees. "It shows him loyal to Reagan, standing up to the extreme voices in his party, and supporting something the American people want." Some see Dole, despite his hesitancy to endorse the treaty, cashing in as Senate Republican leader during the ratification debate. "He has an opportunity to pick up a substantial amount of credit by the way he handles himself in the Senate," said former senator Charles McC. Mathias Jr. (R-Md.).

On the Democrats: At first blush, a successful summit appears certain to cost the Democrats a partisan advantage. "What any kind of arms-control treaty does to the Democrats is to undercut one of the important legs of our foreign policy," said Alvin From, executive director of the moderate Democratic Leadership Council. "We've always been able to argue that Democrats were more likely to negotiate an agreement."

Down the road, Democrats could find compensating advantages. Greg Schneiders, a Democratic consultant, observed that the treaty "allows the Democrats to drive a wedge between Reagan and his party, to say something nice about him, while criticizing his fellow-Republicans" opposing the treaty.

But the larger, long-range point, several observers noted, is that historically, Republicans have profited from public concern about war-and-peace issues, while the economy has been the Democrats' best issue. To the extent that the summit and its aftermath convey the sense that war is a receding danger, rising fears about the future of the economy could well shape the outcome next November.

Presidential pollster Wirthlin, whose findings parallel the Post-ABC Poll's report of growing apprehension about a recession, said, "The danger to Republicans will be on economics, especially if the reality begins to confirm the perception."