THERE'S NEVER any shortage of bad ideas circulating in the political atmosphere, but in this post-election season one stands out. It's the suggestion, advanced by Curtis Gans of the Committee for the Study of the American Electorate, to ban all TV political ads except those in which the candidate stands before a standard solid- color background and speaks for a specified period of time.

At first glance, this sounds like an attractive idea. Almost everyone feels insulted by the notion of political ads featuring talking cows (one such helped reelect Sen. John Melcher (D-Mont.), a veterinarian, in 1982) or showing shot-through-gauze scenes of happy families carrying a rolled-up rug from a moving van into a clapboard Cape Cod (you might remember that one from President Reagan's campaign). What do cartoon-character, feel-good pictures have to do with serious politics? Why can't candidates just stand still and discuss the issues?

For Mr. Gans and others who ask this question the Founding Fathers, almost 200 years ago, had a reply. It's called the First Amendment, and it was intended to allow politicians and their supporters to debate issues and campaign for candidates in any way they please. It didn't take the Founders long themselves to regret some of the tactics which, after reflection, they concluded were protected by the First Amendment. The scurrilous invective of the politics of the 1790s finds almost no echo in our politics today. Neither does the orotund hours-long oratory of the era of Daniel Webster, et al.: try to get a crowd of a couple thousand people, or several million people watching television, to sit still for a three-hour speech today. As political ideas evolved and issues changed, as the nation and the electorate expanded, as the media through ch political ideas and arguments changed, the form and content of political discourse changed. But, at least until now, no one thought that the government should be able to dictate to a candidate how he must campaign.

For, when you think about it, even the glitziest ad can communicate political ideas -- and more of them than you might think. That's because even a 30-second spot builds on and draws from voters' banks of knowledge of facts and political arguments. Before you charge that emotion-laden pictures can convince voters of things their personal experience and knowledge tells them are not true, ask your self whether the Reagan feel-good ad would automatically have worked for President Carter in 1980. We are stuck -- if stuck is the right word -- with a political system in which candidates can campaign and communicate political ideas in any way they want. What's wrong with that?