Halfway through the 1990 primaries, only one incumbent in the House of Representatives has been defeated -- a man already convicted of sex crimes with an underage female. If that's what it's going to take to beat any of them, 1990 may again see more than 98 percent of House members seeking reelection succeed.

Former president Ford, on his annual visit to the National Press Club, warned that the rigidity of the congressional election system was subverting the constitutional design and turning ''the people's House into the incumbents' House.'' Perks, PACs and gerrymandering were the villains he identified.

Far too often, he said, incumbents of both parties have conspired with their allies in the legislatures to draw district lines that safeguard most of them from challenge and reduce the number of competitive or ''swing'' districts to a minimum. In addition, he said, they have expanded their staffs, the number of district offices, their mail and phone budgets to the point that their capacity to communicate with constituents dwarfs that of almost any challenger. Finally, they have converted interest-group political action committees into fund-raising machines for the reelection of both parties' incumbents, further tilting the odds in their favor.

The result, said Ford, is that House elections -- which were designed to register and reflect short-term swings in the political mood and which did that job well as recently as the 1970s -- now have become the most predictable and almost meaningless part of our decaying democratic system.

In the question period, someone asked the obvious query: If the House election system is that bad, isn't it time to limit the tenure of representatives, say, to 12 years? Ford, thinking of the skills of some of the veteran legislators with whom he served in his 26 years on Capitol Hill, said the sacrifice of experience and judgment would be too great. But the term-limit idea will not die. Just the other day, Irving Kristol, editor of The Public Interest and scholar of American government, announced that he was abandoning his earlier opposition and embracing the doctrine of 12 years and out.

The temptation to follow his example is great. But it's still a bad idea and the wrong solution to the stultification of House elections. The advocates have not thought through the consequences as well as Ford did in rejecting it.

A House with a 12-year life cycle would be stripped of its expertise and its institutional memory. As Rep. David Obey (D-Wis.) has pointed out, even though reelection is nearly guaranteed, retirements and decisions to seek other offices have left the House with only 31 members who shared the debates about the Vietnam intervention and only 47 more who experienced Watergate.

The memory of those follies on the part of past presidents is important to the collective judgment of a legislative body -- and would be sacrificed by the 12-year limit.

Unless, of course, congressional staff members were not subject to the same rule. This is a question I have never seen term-limit advocates address. To rotate the membership of the House completely every 12 years while retaining permanent committee staff would have only one consequence: power would shift very rapidly into the hands of that unelected congressional bureaucracy.

But to retire the staff as rapidly as the membership rotates would have an equally clear and undesirable effect: Congress would quickly be drained of its capacity to monitor and influence the career bureaucrats in the executive departments and agencies. No longer would anyone on Capitol Hill know where the bodies were buried -- or even what questions to ask.

In short, term limits for House members would not serve to restore popular control of the government. They would leave the unelected congressional staff members and executive bureaucrats even more in control of decision-making.

Nor would the proposal increase competition for House seats nearly as much as proponents suggest. My hunch is that if House members were limited to six terms, you would find hard-fought contests in some (but not all) of the roughly 75 seats left open by mandatory retirement each year, as you find now in some but not all of the 33 or 34 Senate seats up in each election. Two years later, perhaps half of the 75 freshmen would be challenged seriously in their first bid for reelection. And then, I suspect, most would be left alone for the next four elections, as ambitious politicians in the district decided it prudent to wait another few years for the seat to be open.

That won't increase competition significantly or allow the kind of great national swings Ford recalled from the House contests of such years as 1964 and 1966. The only way to restore competition in House races is to do it directly, by reducing the systemic advantages incumbents have given themselves and increasing the flow of resources to challengers. That means changing the campaign finance laws -- something the incumbents once again seem unwilling to do this year.

Turning up the heat on the campaign finance issue would be a lot more useful than chasing after the mirage of term limits.