IT'S GOING to take the political scientists and econometricians a couple of years to get the numbers exactly right (or as right as they will ever be). But the data reported to and compiled by the Federal Election Commission through the middle of this month give us enough to gauge the magnitude of what could be called the Gross Political Product. It's still less than Americans spend on soap, but it's also a lot more than it used to be.

How much? Well, try half a billion for the biennium beginning in January 1983 and extending, so far, up to last month. The biggest hunk has been spent by the presidential campaigns. In the pre-convention period the eight or so Democrats and Ronald Reagan raised some $91 million (and spent several million more), and the government gave the two major parties $16 million for their national conventions. On top of that, you have $40 million each in federal funds for the Reagan-Bush and Mondale-Ferraro campaigns. That's a total of $147 million for presidential campaigns, not all of which has been spent yet.

Then there are congressional contests. As of Sept. 30, candidates in the 33 Senate races had spent some $95 million, according to the FEC, and candidates in the 435 House races had spent almost $101 million. October is bound to be a big month for campaign spending, and many congressional candidates have long since prepared for that: Senate candidates have $17 million and House candidates $38 million cash on hand. Of course some of that -- like the $572,000 Ways and Means Chairman Dan Rostenkowski has in the till -- is not likely to be spent this year.

Political action committees have spent some $148 million since the beginning of 1983; $57 million of that went directly to federal candidates and most of that shows up in spending figures. A lot of PAC money goes for "independent expenditure" campaigns; Terry Dolan's NCPAC, for example, is spending millions on ads for President Reagan (legal, so long as there's no coordination with the Reagan-Bush campaign) as well as its usual millions on campaigns against incumbent liberal Democrats.

What do we get for all this money? Bumper stickers and matchcovers, hundreds of political headquarters, thousands of phones, leased 727s and DC9s, consultants -- all those things, of course. But most of the Gross Political Product goes, directly or indirectly, to the television advertising that enables candidates to speak to voters directly and to the direct mail pieces that enable campaigns to speak separately to disparate groups. We understand that there is no way to do these things free. But we persist in thinking there must be a better, less extravagant way.