Silver Lining in the Blue Collar: Presidential pollster Richard Wirthlin said yesterday that his recent surveys show President Reagan regaining most if not all the blue-collar support he won in 1980, despite the long recession and the highest unemployment since World War II.

But Wirthlin also acknowledged that the large black voter turnout in recent elections is a "potential problem" for Reagan in 1984 and that the president has not closed the so-called "gender gap" in which women tend to give him lower ratings than men.

Wirthlin said recent trial heats matching Reagan with Democratic presidential contenders Walter F. Mondale and John Glenn show that the president is receiving "about the same degree of support today" from blue-collar voters as he did in the 1980 election.

The blue-collar vote was a critical factor in Reagan's 1980 victory. Surveys showed he received between 45 percent and 47 percent of this traditionally Democratic bloc, far more than GOP candidates generally command.

When the 1981-82 recession sent unemployment skyrocketing to 10.4 percent, some White House officials, and many Democrats, assumed that it would hurt Reagan with blue-collar voters, making him vulnerable in the big Northeast and Midwest industrial states.

But Wirthlin told a breakfast meeting of reporters yesterday that his latest surveys provide "surprising" evidence that the erosion in Reagan's support has not been as serious as believed. Even though blue-collar voters are "under the gun" because of economic problems, they have "kept their allegiance pretty much intact for the president," he contended. Wirthlin noted that polls have recently recorded an upturn in Reagan's approval rating.

At the same time, he said early surveys pitting Reagan against Mondale and Glenn, with the undecided vote evenly divided, show the president still commands between 45 percent and 47 percent of the blue-collar vote. In these trial heats, Wirthlin said his data shows that Reagan runs even with Glenn, and ahead of Mondale, "but not dramatically."

Even though Republicans suffered heavy losses in the industrial states in the 1982 congressional elections, Wirthlin said "Americans generally, and blue-collar workers specifically, do not tag Reagan with being the major source responsible for economic difficulty."

White House officials have talked in recent weeks about developing a Sun Belt reelection strategy for Reagan, and Wirthlin said "there are more blue-collar workers in the South than in the Northeast." Wirthlin also said his surveys show Reagan "doing well" among Hispanic voters, in part because of his hard-line approach to communism in Central America, and that Reagan is doing better among younger and better-educated voters than in 1980.

But Wirthlin added that "there is concern" about "the whole generic issue called fairness," that Reagan's programs have unfairly hurt the poor.