THEY ASKED A SONGWRITER once how he went about writing a song.

"Simple," he said. "I hear it in my head."

They asked a filmmaker once how he went about making a film. "Simple," he said. "I see it in my mind."

There's a powerful line in the Bible I keep inscribed on the inside cover of my appointment book. It reads: "That which is essential cannot be seen with the eye. Only with the heart can one know it rightly." The search for essence is not only what science and philosophy and art are all about. It's what American politics is all about too.

The poll-takers tell us people vote their feelings more than their thoughts. That feelings like hope and fear are more powerful instruments of decision than mere rational judgments of right and wrong. People judge political candidates and officeholders on feelings of trust, on the kind of people they perceive them to be. On the kind of people they want to think of themselves as being. President Reagan projects a joy in being an American. That is why, although he loses on many of the issue polls, he wins every election.

And that is where political media consultants come in on issues like defense spending, the MX and the Strategic Defense Initiative.

They are the ones who will try to translate dry votes in the Congress on issues like these into powerful, emotionally moving broadcasts on television in 1986. They will connect a candidate's vote on an issue with a citizen's vote for that candidate.

For the business of political communication is more a matter of touching feelings than moving minds.

Do issues count? Of course they do, but more as the heart feels them than as the mind dissects them. Give a young man 37 well-thought-out reasons why the girl he is intending to wed is all wrong for him, and the odds are that all your words will stop at the eardrum. Tell somebody who feels prayer in the school is right all of your reasons why it is wrong, and see how far you get persuading that person to leave the Constitution alone. The internal combustion that leads to the bombing of abortion clinics illustrates how powerless the human brain can sometimes be in subduing the passions that seethe beneath the surface.

Media specialists who try to position their candidates against MX and the like, will be facing the problem that they will be airing a negative ad campaign. It's been discovered over the last few campaigns that negative ads just don't work as well as we originally thought. A few years ago, negative campaigns became popular after the National Conservative Political Action Committee claimed that their negative ads were key in sending five or six incumbent U.S. senators back to the farm. The theory developed in the political community that the emotion to tap was not affection for your candidate, but contempt -- or possibly even hate -- for his opponent.

There was really nothing new about this in American political history. Politicians have been calling each other bad names for 200 years. What made the concept of negative communication -- stressing what you are against, -- seem new was the volume of it regurgitating over television in paid political ads.

But the medicine that brought instant health to sagging candidacies in 1980 lost a lot of potency in 1982, when the success rate of those using negative commercials dropped precipitously. The lesson seemed to be you can serve up poison pills, but only with extreme caution and always with a doctor's prescription.

Last year, we grew to appreciate another emotion too long ignored or clumsily portrayed by the political camera. Call it the power of love. It is the love that is felt by an old woman for her congressman who comes through for her in bucking the bureaucracy to see to it that she receives her Social Security check on time. It is the love felt by a blind man for his senator who comes through for him in procuring a license to run his own radio station when everyone else doubted a blind person could handle it. It is the love felt by a Minnesota farmer and a Mississippi teacher for people they could relate to as Rudy and Thad because each of these incumbents (Sens. Rudy Boschwitz and Thad Cochran) had reached out and made the human link that love is made of.

It will take more than a few disagreeable decisions on their voting records to move you away from them.

Some people claim that one of those disagreeable decisions the voters will have to confront is their senator's vote on defense spending. The reasoning goes that all that money spent on defense will be that much less the people will have to spend on themselves, and when they wake up to this fact they're going to be boiling mad.

I don't see it this way at all. In fact, I believe there's an emotion working beneath the surface of these issues which, like a boomerang, will hurl these reasons back to the sender with cruel and incredible force. For lack of a better term, call it the emotion of waiting helplessly for something awful to happen over which you have no control. I know personally what this feeling is all about. I lived it just last month. And I wrote my feelings down.

"There's only one thing in the world that matters. I want my baby well again. The virus for which there is no medicine has seized her lungs. She's two months old and already life is daring her to live."

"The doctor is on the phone. He sounds frustrated and discouraged. 'Ride it out,' he says. 'There's not a hell of a lot anybody can do.'"

"I make a resolution about waiting. If my kid gets well, I'll never complain about waiting again. I will never shout at a red light that doesn't turn green soon enough. I will never complain about waiting in a restaurant to be served -- not even in a dentist's office waiting to be drilled. So the shirts didn't come back from the cleaners in time. Big deal. 'Have a happy day.'

"I'm feeling good about my new-found ideas about waiting until it strikes me that waiting is the greatest sin ever committed by mankind on this earth. Like the 6 million Jews the world left waiting to die. Like those Ethiopian kids the planes left waiting to starve. And now what is the world waiting for? To have somebody named Qaddafi or Arafat or Khomeni blow it up? My God! Waiting helplessly for something awful to happen has all humanity living on Death Row with no appeal in sight."

Well, my little daughter is breathing easily again. (Me too.) And I've gained a personal reprieve and a personal insight. That the feeling of waiting helplessly is terrible. Everyone has it probably at one time or another. In fact, the whole world, whether it wishes to acknowledge it or not, has been waiting that way for 40 years. And it won't go away unless we make it go away.

The senator who is voting for the Strategic Defense Initiative is not waiting helplessly. He's insisting that something very impatient, like the human imagination, do some quick catch-up with the technology of extinction. And he doesn't need hired actors or mirrors to sell his case. He does it standing on his own feet:

High camera angle. We see a "graveyard" of World War II airplanes and a figure (our senator) walking towards us. The crane gently lowers until the senator is at eye level. His narration starts at the top and proceeds as follows:

"This is a place where old war machines come to die. Good plane, this old P-38. Saw its share of misery, I'll tell ya, and gave its share back, too.

"You know -- .

"Wouldn't it be nice if one day all the tools of war were buried once and for all?

"Wishful thinking?

"Well -- think of it this way.

"If we don't bury them -- they will bury us.

(Pause)

"President Reagan says we can build a system of defense that will make nuclear war as obsolete as any of these babies.

"It will cost a lot to build it.

"But what will it cost if we don't?"

(Fade to black and title.)

Yes, they'll say about the SDI what they'll say about the MX. That it costs too much money. That it might work poorly or not at all. That there are better things to be doing with our resources. That the taxpayer is being hoodwinked. That roads need paving, and farmers need saving and school lunch boxes need replenishing. And that they're sick and tired of hearing about defense.

So we'll ask: Would you rather wait helplessly? I think I know what the answer will be.