After John Anderson opened a headquarters in Maryland the other day, I rode back with him to his home in the Washington suburbs. He was hot and tired. "I didn't need to wear this suit," he said reproachfully. Then he heaved a sigh: "Nobody can imagine how much hard work it is, running for president."

The Anderson home is an unpretentious red brick affair in a block of houses so similar they seem to be making faces at one another. The parlor, where we talked, is a small room crowded with the marks of high culture. There are books on the shelves, paintings on the walls and a stand-up piano. The coffee table had a Shakespeare collection and a volume of speeches by Adlai Stevenson.

Mrs. Anderson was away, and Anderson himself had to deal with two little girls -- one five, the other eight -- who were at home. They wanted to go shopping; he put them off for a while. One had left the top off a bottle of Coke Anderson offered to me. "It's probably flat," he said. But it wasn't.

I said that while I had known him for many years, I really had no clear idea of how his mind works. His mood brightened, and he plunged into a quite good imitation of a bang-bang television announcer. "Anderson," he said in deep tones of crisp authority, "thinks like a machine. He has a mind that is coldly analytical, metallic in its precision."

Then he turned serious and reflective. He said that a shaping influence for him had been long experience on the Rules Committee of the House of Representatives. He hadn't become a specialist in agriculture, or foreign policy or banking or anything else. "I'm a generalist," he said.

But he knew about all kinds of issues from taxes through foreign policy to the environment. He knew the interests behind proposed measures and the side effects after legislation was passed. He knew procedures for delaying matters, and the politics of making them happen.

I asked him about substance. Anderson cited his proposal for a 50-cents-per-gallon tax on gasoline as an example of a single proposal that addressed all the country's leading problems. He said the tax would "mean genuine conservation of the most scarce form of energy. It would make us less dependent on foreign oil, and less prone to have to go to war for black gold. By using the proceeds to reduce Social Security taxes, we would both stimulate the economy and curb inflation."

I asked Anderson how he thought he could push through a 50-cent gas tax when Jimmy Carter had been beaten overwhelmingly in the Congress on a proposal for a 10-cent gas tax, Anderson said: "I think it's a matter of presentation. I think people will pay more for gasoline if they're assured there would be a reduction in Social Security taxes. I think it's a matter of plain talk and common sense."

Our conversation drifted around to the campaign. Anderson said he was now concentrating on fund-raising and getting on the ballots in the various states. cThat meant visiting supporters and urging them to give money and sign petitions. In a month or so, he would probably make a European trip. Then he would begin to campaign nationally with a heavy emphasis on television.

I asked him if raising money and working on petitions didn't put him at the mercy of militant partisans, many of them extremely liberal on the social issues. He acknowledged the point.

"I don't want to become the darling of the radical chic," he said. He added that he had broken with Stewart Mott, the General Motors heir who had tried to tilt the Anderson campaign in a radical direction. He said he thought he had a good shot at the blue-collar vote in the Midwest and at the farm vote. He pointed out that he had always had a strong record on defense. When I asked about energy, he said he favored nuclear power and coal as well as solar energy.

We discussed in a desultory way possible vice presidents. He had heard talk of Gov. Hugh Carey of New York, and Sen. Pat Moynihan, and former governor Terry Sanford of North Carolina, and Mayor Kevin White of Boston and even of the former secretary of health, education and welfare, Joseph Califano. Anderson hadn't had much time to think about it. He didn't even know Kevin White.

Someone had mentioned to me that Anderson was going to skip Germany on his European trip. He said that was wrong. He mentioned various West German leaders he had come to know as a member of the Trilateral Commission. gHe reminded me that he had served as a Foreign Service officer in Berlin. He aired a couple of phrases in a German that didn't sound at all bad.

When I left, I had to make a phone call. Anderson was obliged to talk the younger of the little girls into surrendering the phone. I came away convinced -- as I'd been before my visit -- that Anderson was by far the best-qualified of the candidates in the field.

In my judgement, he has the keenest intelligence and the richest powers of articulation. More important, he is the only candidate with a sense of how to make the system work. But along with appreciation of his capacity, I also developed a sense of a man who has to do everything himself, who lacks organization in the worst way, who is seeking to do one of the hardest things imaginabnle virtually all alone.