Richard Wirthlin, pollster for President Reagan and the Republican National Committee (RNC), argued yesterday that survey data and economic trends suggest that the GOP has the potential to use the 1986 elections to become the dominant political party for first time in more than 50 years.

At the RNC's semiannual meeting, Wirthlin and other GOP strategists pointed to a series of pro-GOP findings unprecedented since at least the presidency of Dwight D. Eisenhower, when comprehensive, regular polling began:

*Gains in party identification by the Republicans during the 1984 election have held for 14 months. Wirthlin said that in a Jan. 11-12 poll, Democrats held a 43 percent to 41 percent advantage over the Republican Party, and a separate poll by Robert Teeter's Market Opinion Research placed the Democratic advantage at 46 percent to 44 percent. In both cases, the difference between the parties is statistically insignificant.

*The American public, in sharp contrast to the 1970s, believes that the present is better than the past and that things will get even better.

*From a party that was overwhelmingly dominated by northern white Anglo-Saxon Protestants (WASPs) in the 1950s, the GOP has become geographically and ethnically more diverse, according to the Teeter-MOR survey. Northern WASPs have fallen from 56 percent of the pre-1960 GOP electorate to 32 percent, while Roman Catholics have grown from 10 percent to 13 percent and southern whites have nearly tripled in their standing in the GOP, growing from 11 percent to 31 percent of Republican identifiers. This diversity does not include blacks, who make up 2 percent of Republican identifiers.

*GOP gains among young voters remain firm. The MOR survey found that people from age 18 to 24 give the GOP a 51 percent to 39 percent advantage over the Democrats.

*Unlike past second-term GOP administrations, Reagan's is not facing signs of a recession.

Democratic pollsters responded in different ways to these GOP claims.

Paul Maslin of Hickman-Maslin, conceding that the GOP has made substantial gains in presidential elections, argued that in the 1986 off-year elections, issues such as education and toxic-waste disposal will gain salience. These issues work to the advantage of Democratic candidates, he said. "There is a real dichotomy" between Republican identification in presidential and state elections, he said.

Alex Evans, senior analyst for Cambridge Survey Research, disputed claims that the parties are within 2 or 3 percentage points in terms of voter identification. He said the Democrats have an advantage of 5 to 7 points.

In addition, Evans contended that party identification figures are becoming less valid. "Party ID seems to be shifting around," he said, noting that in the 1985 Virginia election, what had been parity between the parties at the start of the contest turned into a 9-point Democratic advantage by election day.

In some respects, the Teeter-MOR poll showed how framing the agenda for campaign debate has become an essential element of the battle between the two parties.

In the case of domestic social spending, for example, Teeter found that when voters are asked if they support more spending for education and services, they favor spending, 63 percent to 31 percent -- adopting what amounts to a pro-Democratic stance. When voters are asked if the food stamp program is abused and should be cut back, however, they are overwhelmingly for reductions, 77 percent to 18 percent -- adopting a pro-GOP stance.

Similarly, when asked if labor unions are too powerful, the sample public agreed, 65 percent to 30 percent -- a view generally seen as benefiting the GOP. But asked if unions are a necessary part of protecting workers, respondents were prounion by 66 percent to 32 percent.