Let's go over it one more time: if either George McGovern of South Dakota or Hugh Gallen, the governor of New Hampshire, calls with his ideas on changes in the way we choose our presidents, be absolutely sure to take the call and to take notes.

But if any call on the same subject comes in from either of New york's unbashful Democrats, Hugh Carvey or Pat Moynihan, then the call and the caller can be put on permanent hold, with no second thoughts.

Because in the serious matter of nominating presidents, than which there is no more serious political matter, McGovern and Gallen have been grown-up serious players;; Carey and Moynihan, amusing groupies.

George McGovern, facing his third impossible reelection campaign in the last 12 years, did not hesitate to endorse, and to campaign for, Ted Kennedy. It is hard to figure out where McGovern's support of Kennedy helps him with any of South Dakota Republicans or independents McGovern will have to have next November.

Hugh Gallen, who is striving single-handedly to make loyalty a relevant factor in American politics again, chose to remember his debt to Jimmy Carter ffor the president's crucial help in Gallen's uphill fight in 1978. Last October, he endorsed Jimmy Carter for reelection. For anyone who may have been absent last October, Jimmy Carter was then about as popular, both in New Hampshire and the country, as ringworm.

Anyone familiar with McGovern's and Gallen's political precariousness might call the actions of these two men either grounds for commitment or contemporary profiles in courage. What we actually have here are two verifiable sightings of actual political leadership.

It is good to remember Gallen and McGovern as well as Carey and Moynihan, who both chose to watch the action through heavy-powered binoculars from several thousand yards offshore rather than to become involved, because we will be reading and hearing a lot in the next few months about political "leaders" playing a more significant role in the future selection of presidential nominees. After all, the argument will go, the "old" system gave us both Roosevelts and Jack Kennedy and Harry Truman and Ike and Andrew Jackson, and what has the "new" way given us but Jimmy Carter, that same George McGovern and now Ronald Reagan?

Well, let's do look at the record. The old system did provide us with a few men who belong on the taxi squad of history: Grant, Harding, Tyler and Fillmore. But the argument that is made so strongly for the advice and consent of officeholders and party leaders in the selection is that the leaders know these fellows, the candidates, so much better than the rest of us do or can. They know how the candidates respond to pressure, whether their word holds in private and if they have the stuff of presidents or just of presidential candidates. Makes sense.

Until you remember that in the history of the republic only two men have been nominated for national office five times by either of the major parties. Of course, everyone remembers FDR. But how about Richard Nixon, of recent and fond memory? Like Roosevelt, he ran five times and won four and lost one. He was nominated basically without significant opposition from within his party, from those who knew him best. You can say what you want about George McGovern or Jimmy Carter or Ronald Reagan and some of their blemishes. But not one of these follows has given us anyone approaching G. Gordon Liddy, the Julia Child of rat au vin. None of these three has been available on tapes for $9.98, giving directions on the mugging of the Constitution and how to pay for it No, Richard Nixon, among his other achievements, all but destroyed the argument about the valuable insights that the office-holders and the party leaders could provide the rest of us, on the periphery, about the candidates and their true character away from the teleprompter.

If Gallen and McGovern or Gov. Milliken of Michigan want to offer some advice on improving or modifying the presidential nominating system, let's give them a full hearing. But the neutrals from 1980 can save themselves the effort, and the rest of us the time, thank you.