For the next six weeks, you may see a lot of Ed Behler and Edwin Steffe on television. Their names are not familiar, but you should recognize the faces: these are the actors the Republican Party has hired to play Jimmy Carter and Tip O'Neill in a $1.7 million advertising campaign to be beamed into 56 media markets this season. The Republicans are crowing about the ads. They believe that a similar ad in 1980, with Steffe playing Speaker O'Neill driving a car that ran out of gas, helped convince voters that the Democrats were the party of old ideas and failed leadership.

But the Carter-O'Neill ad sends another message. The O'Neill-out-of-gas ad worked well two years ago, when the Democrats were in power and the Republicans, as the opposition, could run against things as they are. But the fact that the Republicans are running this kind of ad now, when they are the party in power, is a confession of weakness.

You can be sure that decisions on how to spend $1.7 million are not made casually. They are made after intensive polling and careful study of public opinion. The Republicans evidently have decided that an advertising campaign exclusively devoted to the virtues of the Reagan program would not be credible. Instead, they are reduced to the argument that the other guys were even worse.

This may be good politics in the short run. American voters find negative messages credible-- and familiar. Our politics for the last dozen years has been characterized by a corrosively negative tone that has made it difficult for incumbent parties to get credit for their accomplishments and easy for the opposition to excoriate incumbents for their shortcomings. In that time, one president has been ousted, two have been defeated, and none has been able to imprint on the public mind his vision of the role of government as Franklin Roosevelt did in the 1930s.

But in the long run, it is in the interest of a party in power to establish a positive dialogue--to focus public attention on issues about which people have positive feelings, both about the general direction of the nation and about the performance of the incumbent administration. Ronald Reagan, more than his recent predecessors, seems interested in establishing a positive dialogue. He wants Americans to think well of their country, to appreciate its strengths and celebrate its successes with the kind of fervor they have devoted lately to decrying its weaknesses and bewailing its failures. In the 1980 campaign, candidate Reagan and the whole Republican Party did more than attack the Democrats; they articulated a vision of a stronger, more prosperous, more productive America and advocated policies that seemed to many voters likely to make that vision a reality.

Now, with high interest rates choking off the recovery that was implicitly promised and with apparently endless deficits keeping interest rates up, the Republicans can do no better than argue that the Democrats would have done even worse. An administration that feels forced to rely primarily on negative campaigning is an administration in trouble: remember how Jimmy Carter's campaign in 1980 seemed reduced to emphasizing that he was younger than his Republican opponent and had a better driving record than his Democratic challenger?

This year, the Republicans are also producing some positive ads, stressing the lowering of inflation and saying that "Republicans are beginning to make things better." But the prominence given the Carter-O'Neill ad--and the fact that it was chosen to appear first--sets a negative tone. Once the negative tone has been set, it is hard to establish a positive dialogue. The Carter-O'Neill ad may help the Republicans marginally in 1982, but it is a setback rather than a step forward in the attempt, which is in the Republicans' patriotic as well as partisan interest, to change the fundamental tone of American politics.