WINNING the White House and successful political party-building are not the same thing. With the national party conventions coming up this summer - July for the Democrats in San Francisco, August for the Republicans in Dallas - it is helpful to keep this in mind.
In writing the party platforms, staging debates and hearings on the full range of domestic and foreign issues, writing fund-raising appeals and ad campaigns, the major parties should try to reverse the decline of their effectiveness seen in recent years. Now is the time to recast their appeal to a changing American public.
Both parties are having the most trouble at the moment with the political center.
Democratic front-runner Walter F. Mondale, for example, is given healthy 2 -to-1 favorable ratings for leadership qualities by the party faithful, according to the Harris survey; but among Republicans and independents, his positive rating is reversed.
Kevin P. Phillips, the thoughtful Republican political analyst, reminds his party that its success in capturing the White House in 16 of the past 20 years has not translated into any substantial recruitment of voters to Republican ranks.
John B. Anderson, who reportedly will not try to repeat this fall his 1980 run for the White House as an independent, still argues that there is a place for a new centrist party. Political tides, he claims, pull the GOP increasingly into the party of ''the rich'' and the Democrats into the ranks of ''the poor.'' ''We need a middle force in America devoted to holding the center together and to bringing into it all who wish to be there,'' he says.
The professionals of both major parties are fully aware that party-building occurs over decades, not in the two-year and four-year cycles of legislative and presidential elections. The Republicans are trying to make inroads among blacks, labor, women, Hispanics, Jews. The Democrats have massive registration drives under way. They're catching up to the Republicans on computer expertise. Still, both parties seem mired in their own stereotypes of the past.
Mr. Phillips puts it this way for the Republicans: ''The Republicans' economic sobriety and commitment to national defense must somehow be institutionally broadened and infused with a sense of the common man. If it is not, the GOP will lose another historic opportunity to include dissaffected Southern, Western, and blue-collar Democrats.'' The party must appeal, he said in the New York Times, to ''the populist sentiments of these restive Democrats - their preference for 'little guy' economics and for a moderately 'activist' Government.''
Other analysts phrase it differently. They refer to the Republican Party's ''fairness'' problem. Or the persistent image of ''country club Republicanism'' - reflecting white, upper-middle-class values. Although such Republicans may be small in numbers in the broad sweep of Republican voters, the impression remains that they have set the leadership style of the party.
A lack of ''a crusading egalitarian style'' in elections at all levels has kept the GOP from taking full advantage of powerful shifts in religious, economic, and social attitudes the past two decades, argues political scientist Evertt C. Ladd. And S.I. Hayakawa describes the Republicans' profile as ''insiders'' and the Democrats as ''outsiders.''
For their part, the Democrats ideologically remain on the defensive. Gary Hart's early surge could be at least partly explained by voters' satiety with New Dealism. The party as a whole has not caught up with changing attitudes on protectionism. It seems stuck in the image of ''factory town'' America, unaware of the emerging electronic technocracy.
Neither ''country club'' nor ''factory town'' fairly represents America today. Shifts of population, the extraordinary rise in college education, an economy that relies more and more heavily on world trade, a culture thriving artistically at all class levels - these hardly suggest an America standing still, or stuck in the economic divisions of the 1950s.
Presidential contests can too easily overwhelm the broader range of political responsibilities in an election year. The parties should guard against this in 1984 and tap the potential for change, the underlying dynamism in the public, as they prepare for the summer conventions and the fall campaign.