On the short list of America's national personality traits, optimism is right at the top. Americans have traditionally welcomed change as basically another name for improvement. We may write songs about the good old days, but we have usually known that today was better than yesterday but probably not as good as tomorrow. But now, according to a just-released national survey done for the Democratic Congressional Campaign Committee by pollsters Peter Hart and Dotty Lynch, Americans have some very serious concerns; we may be more fearful than cheerful, and that may be very good news for the Democrats in 1984.

The poll of 1,032 registered voters, in addition to showing the Democrats with a big edge in next year's congressional races, reveals the fear sthat currently plague American voters and inevitably shape American politics. In 1968, our fears were for personal safety at a time of riots and lawlessness as well as fears of cultural and racial change in the nation. In 1983 our fears are about an uncertain future.

Of highest concern to Americans right now, according to the poll, is the fear that "government programs like Medicare will not do enough to help the elderly afford decent health care." In second place is the apprehension that the "U.S. is heading toward military involvement and war in Central America." (The survey was completed before the downing of the Korean airliner and before the marine deaths in Lebanon.) Next was the fear that large budget deficits will push interest rates up again and the concern that the government will not do enough to protect the environment and to deal with the problem of hazardous waste.

If Medicare were to become in the campaign of 1984 what Social Security was in the 1982 campaign, then the Democrats would almost surely propser at the polls. Voters trust the Democrats more than they do the Republicans to help the elderly as well as to protect the environment. In 1980, the perceptions of the two parties were dramatically altered: the Republicans were viewed by voters as the party of prosperity and the Democrats were seen as the party of peace. Today voters who in 1981 gave the Democrats only a 10-point advantage over the GOP on "putting a limit on the nuclear arms race" give the Democrats a higher score by 50 percent to 18 percent.

The Democrats, bereft of great visions or noble mission, could win in 1984 by allaying voters' fears about a potential loss of economic security and about military involvement. The Republicans, who won the White House in 1952 and 1968 while running against unpopular Democratic war policies, now risk defeat in 1984 on that same war-and-peace issue.

Ironically, the Democrats, who dominated the nation's politics for years with dreams and schemes could win in 1984 by promising (believably) to protect what people have been promised by earlier Democratic presidents. Personal safety and security concern Americans, and the Democrats offer themselves as political security blankets on a platform not of high adventure but of protectionism. In 1984 the Democrats' best hope could be fear.