The next Reagan-Mondale debate suddenly looks far more important. So does the Bush-Ferraro clash on Thursday. President Reagan is still heavily favored to win the election next month. But two other crucial Reagan goals now appear to be at risk because of Walter Mondale's strong showing in the Louisville debate.
Experts say the race now could tighten, and that could cost Mr. Reagan his chance for a strong mandate. Until this moment, it appeared that the President was headed for a thumping victory - one that could have seen him carrying virtually every state.
White House officials were hoping that a big Reagan margin would bring along 25 to 35 new Republicans in the House of Representatives. That would be enough to give the President ideological control of that chamber. With Republicans already in charge of the Senate, the President would have been able to write his own ticket on Capitol Hill.
Reagan would have enjoyed freer sailing on military spending and could have clamped tighter controls on domestic spending. He also would have been in a better position to move ahead with his social agenda, including school prayer, anti-abortion legislation, and support for tuition tax credits for parochial and private schools.
A narrow Reagan victory could have a second deleterious effect on Republican hopes, says David Chagall, who writes a political newsletter in California.
Mr. Chagall observes that the number of Americans who identify themselves as Republicans has been rising in recent months. Some Republicans hope the shift signals a long-awaited realignment of the parties, with the Republicans moving out front as the country's largest political party for the first time since the days of Franklin D. Roosevelt.
Such a realignment ''could be nipped in the bud,'' says Mr. Chagall, for a significant part of the Republican gain is based on voters identifying themselves with a strong Republican President. Says Chagall: ''Reagan needs to show he has a vision for the future that is going to take the country to greater heights than ever.''
Only if the President is able to inspire will he be able to motivate Democrats and independents to make the switch to the Republican Party, Chagall says.
What should Reagan - as well as Mondale - do in the second debate? Chagall and a number of other experts such as media specialist Jerry Rafshoon (a former adviser to Jimmy Carter) say the path for each man is fairly clear.
Reagan must get tough, they say. Several experts were flabbergasted that the President passed up several golden opportunities to whack Mondale. Reagan never mentioned Mondale's ties to labor unions. He said nothing when Mondale promised to do away with tax indexing, which helps middle-income voters. He failed to point out that Mondale favors protectionism for a number of industries - policies that would raise prices on autos and other products for American consumers.
''Reagan was laying back too much,'' says Chagall. ''He was being the nice guy. His advisers apparently told him that being loved was his strong suit.''
Next time, the topic will be foreign policy. Reagan must nail Mondale, these experts say. He must point out such things as the demoralized conditions of the armed forces under the Carter-Mondale administration, US losses around the world , and the Iranian hostages, they add. Mondale must be made to look weak. Reagan could point out all the weapons programs that Mondale opposed as a senator. Reagan must also give some idea of where he is taking the country in its relations with the Soviets, and reassure those worried about a nuclear war, they say.
Mondale needs to stay on the attack, they say. Certain areas clearly offer opportunities: the arms race; the lack of US-Soviet talks; war in Central America; waste in the military; anxiety about nuclear weapons.
Mr. Rafshoon, a Democrat, was clearly delighted with the first debate. ''It was almost like Mondale played Reagan, and Reagan played Mondale,'' he says.
The difficulty for Mondale is that ''right now America wants to feel good,'' Rafshoon says. Reagan has been able to appeal to that desire during most of this campaign. Mondale has not. If Mondale sounds too gloomy about nuclear arms, the Soviets, and Central America, it could play right into Reagan's hands in their next confrontation. Rafshoon says the key for Mondale will be to ''show he is a leader, and make Reagan weasel on the future.'' Rafshoon, like some other Democrats, has one main regret now: ''If only this first debate had been five or six weeks ago....'' If it had, Mondale could be very close to Reagan by now instead of 20 points behind, Democrats say.