REPUBLICANS have won four of the last five presidential elections. But as the party faithful gather to crown their nominee this week, there is an underlying uncertainty about their fortunes in 1988. It stems in part from these factors: The Republican Party has lost some strength since 1984, when a ``realignment'' of political parties was widely heralded. Republicans, besides the presidency, hold 23 governorships today, including such key states as Texas, California, and Florida. GOP voter registrations are up nationwide.
But although the gap between the Democratic and Republican Parties has narrowed, the Republicans have not gained majority status, and it is far from certain that the huge support that crossover Democrats, especially blue-collar ethnics, and independents gave Ronald Reagan in 1984 can be transferred to George Bush, who does not carry the same appeal.
The largest segment of the American people still label themselves ``conservative'' (roughly 40 percent). But polls show that Americans today want a slightly bigger, more affirmative role for government in Washington. Some analysts believe that the conservative ascendancy of recent years has peaked.
``The tide has begun to recede and we're seeing a transition to something else,'' says Kevin Phillips, editor of American Political Report, a conservative newsletter. ``It's not just eight years of Ronald Reagan but a changing cycle. ... There's no reason for blue-collar workers to be interested in George Bush. The basis of the conservative coalition laid down in '72 does not apply in '88.''
The voters in that coalition, Mr. Phillips argues, were concerned about such issues as a US sellout in Vietnam, racial and other minority quotas, big government, rising taxes, a weakened defense.
Now they're worried about health insurance, college education for their children, drugs, and possible loss of US economic preeminence to Japan.
Even representatives of the conservative right say that Reagan-style economic conservatism is over and that voters will be looking for the best manager of the nation's problems.
``The way the conservative movement came up through the '50s, '60s, and '70s - that era is over,'' says Paul Weyrich, chairman of the Free Congress Political Action Committee. ``Reagan-type conservatism will not be the conservatism of the future. It is clear the public wants activist government and those people that have solutions to real problems will be given a chance to govern.''
Not all political analysts see sharp ideological distinctions in the country, however. American voters, many argue, tend to be in the middle of the spectrum, with periodic swings toward more or toward less government activism.
``Everyone talks about conservative and liberal tides, but they are talking smoke,'' says John Petrocik, a professor at the University of California. ``A receding `tide' simply means a receding tide of antipathy to government. It's a cyclical thing.''
``The agenda has shifted in the direction of the Democrats,'' says William Schneider of the American Enterprise Institute. ``People want a more activist government, more d'etente with the Soviet Union - and that's due to the success of Ronald Reagan. Now 60 percent of the voters want change.''
How to respond to the desire for change and yet keep voters in the GOP column is the challenge confronting Republicans this year.
Party officials are encouraged by registration figures showing that the Democrats have lost ground, especially in Southern states where race is a dominant factor.
According to the Washington-based National Journal, Democratic registration in Florida has dropped 100,000 since 1984 while Republican registration has risen by almost 500,000. The Democrats still lead in Florida, where the voting-age population has grown significantly, but the lead has narrowed.
Figures for Louisiana and North Carolina show similar gains for the GOP. And in California Republican registrations are up 3 percent while Democratic registrations have dropped 2.4 percent since 1984 (though Democrats are still in the majority).
Not all states register voters by party, however, and registrations do not necessarily translate into voter turnout. A more meaningful measure of potential strength at the polls is party identification: whether voters consider themselves Republican, Democratic, or independent. By this measure, the Republican Party appears to be losing ground.
``Since '84 there has been incremental bleeding,'' says Mr. Petrocik. ``The Republican Party has gone through bad times - the Nicaraguan and Iran-contra affair did us no good.''
Identification of voters with the GOP, especially among lower-income voters, has fallen since '84 and '86, Petrocik says. The so-called ``dealignment'' of the parties, or the growth of independents, is also over.
Frank Fahrenkopf Jr., chairman of the Republican National Committee, maintains that the two parties are now roughly equal and that a realignment of the parties has taken place.
While the Iran-contra scandal eroded GOP support, he says, the Republicans have again closed the gap to within 6 or 7 points of the Democrats. Young people, he adds, continue to move into Republican ranks.
``Fundamentally we're at parity,'' Mr. Fahrenkopf says. ``And we're out-registering the Democrats 2 to 1 among young voters.''
The latest Gallup poll, however, shows the Democratic Party leading the Republicans by 43 percent to 29 percent, a 14-point spread. The narrowing that took place in 1984 following the Reagan election victory has ended.
Election analysts also note that while the Republicans have scored consistent gains at the presidential level, the party has not expanded its base. In 1986 the Democrats regained the Senate and they still control the House.
``This is not an ideological realignment,'' says Curtis Gans of the Committee for the Study of the American Electorate. ``The natural forces pent up in the South are now playing themselves out in the two-party system, with blacks moving into the Democratic Party.
Whatever their nominal party affiliations, Americans today are less party-oriented and increasingly willing to split their ticket. The advent of the primaries, the end of the system of dispensing patronage through the parties, and the television revolution have served to weaken the parties and party loyalties.
``What really has happened is `unalignment,''' says election expert Richard Scammon. ``Many people - labor, for instance - have remained nominal Democrats but are willing to cut the ticket.''