Ronald Reagan is again taking on Jimmy Carter. As the well-choreographed GOP convention awaits the President's acceptance speech tonight, Republicans are framing the main issue around which they want the election to be fought: the difference between what they call the ''strong'' leadership of Mr. Reagan today and the ''weak'' leadership of a Walter Mondale pinned to the past.
When the energized Republicans go out on the hustings, political experts say, they'll be asking, ''Are you better off?'' But they will also be harking back to how Americans felt more than four years ago under the Carter-Mondale presidency.
''If the election does get close,'' suggests political scientist Norman Ornstein of the American Enterprise Institute, ''the Republican pitch will be that it's better to have the leader you know than someone who is mushy.''
''For some time, the preference of the Reagan campaign has been to rerun the 1980 election,'' says political analyst Charles Jones of the University of Virginia. ''This (strategy) requires some of the same issues'' that arose in 1980. Ironically, he says, a key Republican issue is likely to be ''the big deficit, which remains as a symbol of big government and which (Republicans) want to identify with past administrations.''
By contrast with the Democrats at San Francisco, who raised concerns about deficits, war, and the nation's future, the Republicans here have chosen to accent the positive. They are infusing their pronouncements with the themes of optimism, confidence in the future, and peace through strength.
Other issues, however - such as abortion and women's rights - are being played as much to the public outside, it seems, as to the audience inside the Dallas Convention Center. Reagan strategists want the GOP convention to convey party unity to the electorate beyond Dallas. But they also need to whip up the enthusiasm of Reagan's conservative troops by giving a nod to issues that don't always reflect the Republican rank and file.
On foreign policy, for instance, United Nations ambassador Jeane Kirkpatrick strongly attacked the Soviet Union, ticking off its record of aggressive actions. She got more reaction from the convention delegates than did speakers who attacked Walter Mondale.
When it comes to playing foreign policy to a broader audience, however, political experts believe Reagan will leave most of the hard-line rhetoric to his surrogates while he continues his more moderate line of recent months: a willingness to talk with the Soviets and a desire for an arms-reduction agreement.
According to polls, Reagan does least well among voters in the field of foreign policy in comparison with other issues. The majority of Americans favor a nuclear freeze, for instance, which the President strongly opposes.
Democratic strategy for the election campaign revolves around the ''four F's'' - fairness, fear, family, and Ferraro. Whether Mr. Mondale can surmount the political setback caused by the furor surrounding financial disclosures of his vice-presidential running mate remains to be seen.
So far, GOP officials have tried to avoid getting too deeply into the issue, even while pointing out that the Ferraro problem reflects on the judgment and leadership capabilities of Mondale.
On other Democratic campaign themes, however, GOP leaders have clear-cut responses.
Look at the Carter-Mondale years, they say: double-digit inflation, 21 percent interest rates, and ''economic misery.'' ''Is that what Mr. Mondale meant in San Francisco when he talked about 'fairness'?'' asked GOP keynote speaker Katherine Ortega.
Former President Gerald Ford and other convention speakers charge that Mondale is ''peddling fear,'' trying to invent a ''trembling, despairing, miserable America.'' By contrast, they boast, ''Ronald Reagan's America'' includes an economy on the move, more and more jobs, a cut in income taxes, and a stronger America.
For the moment, political observers say, the Republican debate is largely about attitudes and feelings: despair vs. hope, fear vs. confidence. ''The Republicans are trying to paint the Democrats as merchants of gloom, and that will continue,'' says James David Barber, a political analyst who studies the presidency.
But, he adds, a debate will emerge later about ''facts'' - such as the impact of defense spending on combat readiness.
At the same time, experts say, it has been hard for the Democrats to engage the President on the issues in any substantive way. GOP strategists keep the focus largely on Reagan's personality and leadership.
The campaign will revolve largely around ''how people perceive a candidate - whether he is weak or strong,'' agrees Sen. Nancy Kassebaum (R) of Kansas. ''It is a matter of feelings. People don't want to rock the boat, they want to continue in a certain vein,'' when the nation's outlook has been brightening.
This is why Mondale is trying to goad the President into discussing the tax-increase issue. He would like Reagan to take his gloves off and get into the political trenches.
''On the issues, it is the Democrats who will have to take the initiative,'' Mr. Jones says. ''Otherwise, the Republicans will emphasize what Reagan has done for the economy and defense. To get too specific about the future and to take new initiatives is a bit dangerous. Reagan will run on his record.''
His surrogates are making the point.
''America's choice this year is not just between Ronald Reagan and Walter Mondale,'' Sen. Howard H. Baker Jr. of Tennessee told the Republicans. ''It's between a team that has proven it can succeed and a team that has proven it can't.''