For those of us who have been convinced for most of this decade that the presidential selection system has taken a fundamentally wrong turn, there are a few heartening signs that the long-awaited rethinking of the "reforms" of the 1970s is beginning.

In the space of six days, earlier this month, two thoughtful and influential Democrats weighed in with articles making an essential and little-understood point: The frustration many Americans have expressed with the choices they have been given in recent presidential elections and the disappointment they feel with the performance of recent presidents stem directly from the changes that have occurred in the presidential nominating system.

Newton N. Minow, a Chicago lawyer and former chairman of the Federal Communications Commission, made the case in The Wall Street Journal.David Lebedoff, a Minneapolis attorney and longtime leader of the Minnesota Democratic Farmer-Labor Party, wrote a parallel brief for the Washington Post.

While differing somewhat in their suggested remedies, both men put their fingers directly on the heart of the problem. The changes in the nominating rules made in the 70s effectively eliminated any real screening of the presidential hopefuls by the people who are best able to judge their talents and shortcomings -- namely, the politicians and officeholders who have worked with them over a period of years.

"The pros," as they were called, dominated the makeup of the nominating conventions until this past decade. Then, in the spirit of reform and with the belief that broader participation might make the conventions "more representative," the system was changed to encourage a lot more amateurs and average citizens to join in the selection process.

The main device was to switch from selecting delegates in relatively closed caucuses or conventions, where past party service and public leadership credentials count, the primaries, where everyone's vote is equal to everyone else's.

There are two things wrong with this switch. First of all, the primaries themselves are very unrepresentative processes. As Minow pointed out, President Carter's great "victory" in the New Hampshire primary was achieved with the support of 7 percent of the people who voted in the 1976 general election in that state.

The second problem is that even that unrepresentative fragment of the citizens has little chance to learn or judge the real qualities of the candidates they are considering. Their exposure consists of a single meeting, a handshake, a glimpse of the television tube.

As Lebedoff pointed out, candidates who seek the nomination in such a system quickly learn to display those qualities that are most easily communicated in that brief exposure each possible voter gets.

As a proxy for competence, the candidates show off their detailed knowledge of even picayune issues. As a proxy for emotional stability, they show themselves deliberately low-key. As a proxy for leadership, which always risks being devisive, they learn to read and echo the polls.

And, as Lebedoff argues, the very qualities that serve them so well in the primaries -- fascination with detail, a lack of passion, a preoccupation with polls -- are the qualities for which they are criticized when, as presidents, the people finally have a chance to judge their real abilities.

The point of the Minow and Lebedoff articles -- and of this one -- is not to heap more abuse on Jimmy Carter, who currently is being blamed for more evils than any one person could have caused. The point is that as long as we have this kind of selection process, his is the kind of presidency we are going to get.

It is too late to change the selection system for 1980. But the discussion represented by the Minow and Lebedoff articles cannot begin too soon, if the changes are going to be made by 1984.

Because most of the nominating rules were rewritten and most of the primary laws passed by Democrats, it is appropriate that the debate begin there.

But there are also hopeful signs on the Republican side. The pre-primary presidential preference poll being conducted by Florida Republicans this fall represents the ultimate absurdity of the new system. A lottery is being run among those who turn out at county meetings to see who gets to vote in the November preference poll. Candidate organizations are spending thousands of dollars to turn out a few hundred bodies at the caucuses, in hopes of winning the lottery.

No one could possibly pretend this is anything but a parody of a sensible presidential selection system. And most of the candidates and campaign managers, to their credit, despise it. "I wish we could kill the guy who thought of it," one of them told me, sounding as if he meant it.

Don't kill the guy. Change the system. If not for 1980, then surely for 1984.